6 Syntax

Learning Outcomes

After studying this chapter, you should be able to discuss:

  • the basic definition of syntax
  • the parts of speech, including open and closed classes
  • the definition of a phrase and different types of phrases
  • X Bar Theory
  • the definition of a sentence and how to diagram one
  • the tests for grammaticality
  • the different types of grammar
  • the acquisition of syntax


The main goal of syntax is the study of sentence structure and the statement of rules and principles that determine how sentences are built. Here is a quick video introduction to syntax:


In general, two levels of syntactic analysis are distinguished:

  • The formal level analyzes the shape and internal structure of the units in sentences or sentence constituents. This level identifies different word classes, kinds of phrases, and various sentence types.
  • The functional level deals with the role that a word or other unit fills in relation to other elements in its construction. On this level, we find the different syntactic functions.

Syntax tells us what categories words can be sorted into and how those categories work together. Native speakers of a language naturally understand how word categories go together. In linguistics, we call this grammaticality. If a sentence is grammatical, that simply means that the word categories are used correctly. However, sentences might be grammatical and not make sense.

The poem “Jabberwocky,” by Lewis Carroll, is a good example. Note the first stanza:

’Twas brillig, and the slithy toves
      Did gyre and gimble in the wabe:
All mimsy were the borogoves,
      And the mome raths outgrabe.
While the sentences are semantically odd, they are clearly written in English. We know this because our mental grammar notes that the words fit into our understanding of how categories of words should be used. For example, our minds know that “gyre” and “gimble” are verbs and that “wabe” is a noun, just because of the way the words are used.
This demonstrates some important ideas. First, it tells us that our mental grammar understands how words are categorized in English based on their placement in a sentence. In addition, it tells us that our mental grammar must be able to accommodate the creativity of language by having broad categories that can be combined in an infinite number of ways.

Check Your Understanding

Words/Word Classes

Words may be sorted into word classes or parts of speech. Members of the Indo-European group of languages have been analyzed in terms of such categories since classical antiquity. The central principle of this classification is a paradigmatic one: words that can occur in the same syntactic context share the same word class.

There are various views about the taxonomy of word classes:

  • The traditional view
    …defines a relatively large class of different word classes.
  • The structuralist view
    …elaborates this approach and classifies word classes on a higher level, allowing a much more general approach towards syntactic categorization.

As we look at the two approaches, you may notice that the parts of speech look a little different from what you learned in your previous courses. In English, we generally include the following eight parts of speech: nouns, pronouns, verbs, adjectives, adverbs, prepositions, conjunctions, and interjections. The traditional approach separates articles from adjectives and auxiliary verbs from verbs. Interjections are mentioned, but a new category, numbers, is also mentioned. The important thing to remember is that there are different approaches, but all of them attempt to classify words according to some system of classes.

The Traditional Approach

According to the traditional view, syntactic categories (word classes) can be grouped into two general sets:

(limited in number)
  • prepositions (e.g. in, on)
  • articles (e.g. a, the)
  • pronouns (e.g. that, who)
  • conjunctions (e.g. and, or)
  • auxiliary verbs (e.g. be, have)
(theoretically unlimited in number)
  • nouns (e.g. man, table)
  • verbs (e.g. go, see)
  • adjectives (e.g. quick, happy)
  • adverbs (e.g. quickly, rather)

Two lesser categories, numerals and interjections, as well as a small number of words with unique function (e.g. particles) may be added to these.

Note that some words, for example play, occur in more than one word class.

The Structuralist Approach

This view defines word classes in a more general way and thus allows a more general approach towards syntactic categories.

(limited in number)
  • prepositions (e.g. in, on)
  • determiners (e.g. a, this)
  • complementizers (e.g. that, who)
  • conjunctions (e.g. and, or)
  • inflectional elements (e.g. -ed, -ing)
(theoretically unlimited in number)
  • nouns (e.g. man, table)
  • verbs (e.g. go, see)
  • adjectives (e.g. quick, happy)
  • adverbs (e.g. quickly, rather)

Again, a small number of words with unique function, interjections and particles, may be added to these.

The three syntactic categories of nouns, verbs, and adjectives, are called open-class categories. The categories are considered open because when new words get added to the language, they are almost always in one of these three categories — the categories are open to new members. These categories are sometimes also called lexical categories or content words because these categories are the ones that do most of the lexical semantic work in a sentence: they convey most of the meaning of a sentence.

Nouns, Verbs and Adjectives: Open Class Categories

In linguistics, we observe how parts of language behave. When we find a set of words that all behave similarly, we can group them into a category, specifically, into a syntactic category. You might have learned about some of these categories as “parts of speech.”

You’ve probably learned, for example, that nouns are words that describe a person, place, thing, or idea. But, when we’re studying morphology and syntax, we categorize words according to their behavior, not according to their meaning. There are two elements to a word’s behavior:

  • What inflectional morphemes does the word take?
  • What is the word’s syntactic distribution? In other words, what position does it occupy in a sentence?


What behavior can we observe that allows us to categorize words as nouns? Looking at the inflectional morphology, we observe that most nouns in English have a singular and a plural form:



tree trees
book books
song songs
idea ideas
goal goals

English uses a plural morpheme on a noun to indicate that there is more than one of something. But there is a subcategory of nouns that don’t have plural forms. Mass nouns, like rice, water, money, and oxygen, refer to things that aren’t really countable, so the nouns don’t get pluralized. Nouns that refer to abstract things (such as justice, beauty, happiness) behave like mass nouns, too.

If they don’t have plural forms, why do we group them into the larger category of nouns? It’s because their syntactic distribution behaves like that of count nouns. Most English nouns, singular, plural, or mass, can appear in a phrase following the word the:

the tree, the trees
the book, the books
the song, the songs
the idea, the ideas
the goal, the goals
the rice
the money
the beauty (e.g., the beauty of the scenery)
the happiness (e.g., the happiness of the children)


In their syntactic distribution, pronouns (I, me, you, we, us, they, them, he, him, she, her, it) do the job that noun phrases do. A pronoun rarely appears with the, but it can replace an entire noun phrase:

The woman read the book.
She read it.

We’ll group pronouns into the larger category of nouns, remembering that they’re a special case.


Verbs behave differently to nouns. Morphologically, verbs have a past tense form and a progressive form. For a few verbs, the past tense form is spelled or pronounced the same as the bare form (infinitive).

bare form past tense form progressive form
sing sang singing
think thought thinking
stay stayed staying
bake baked baking
remember remembered remembering
read [ɹid] read [ɹɛd] reading
set set setting

Every English verb has five different forms, but only two of the forms have a tense feature. The tensed forms are indicated with a morphosyntactic feature, either [+past] or [-past].

bare/infinitive (non-tensed) eat walk sing take
[-past] (tensed) eats walks sings takes
[+past] (tensed) ate walked sang took
past participle (non-tensed) eaten walked sung taken
present participle (non-tensed) eating walking singing taking

Let’s consider a simple sentence, Jamie might bake cupcakes. This is a perfectly grammatical English sentence. If we change the verb bake to the verb eat, our sentence is still grammatical, Jamie might eat cupcakes. And that makes sense of what we know about how categories work — we group verbs together into the verb category because they behave the same way.

But what about these sentences?

Jamie might arrive cupcakes.

Jamie might hope cupcakes.

Are these grammatical? My mental grammar doesn’t generate these, and I bet yours doesn’t either. And their ungrammaticality isn’t just a matter of them not making semantic sense, either. Since the verb arrive often has something to do with a location, we could try changing cupcakes to Toronto, but the sentence is still ungrammatical: the grammar of English does not generate the sentence, Jamie might arrive Toronto. But why aren’t these sentences grammatical?

It’s something to do with the verbs themselves. Within the large category of verbs, we can group verbs further into subcategories according to the kinds of complements they take. The subcategory information tells us what kinds of complements each head will accept. So let’s look at a few verb subcategories.

Transitive Verbs

Transitive Verbs have one complement, a noun phrase, so they have this basic structure. The verb baked is transitive when it has a complement like cupcakes. Here are some other transitive structures:  drank coffee, likes Linguistics, needs money, speaks Mandarin.


When there is a noun phrase in the complement of a verb, we call it the direct object. And the direct object doesn’t have to be a single word. It could be a fairly complex phrase itself. As long as it’s a noun phrase and it’s the complement of a verb head, we call it the direct object, and the verb is a transitive verb.


Intransitive verbs have no complement at all. These are verbs that describe an action or state that involves just a single participant, like sneezed or arrived or dances or slept.


There’s a small set of verbs that are called ditransitives. They’re a little special because they have two complements, a direct object and what you’ve likely heard called an indirect object. For them to count as ditransitives, they have a special kind of behavior, called the dative alternation. The best example of a ditransitive verb is the verb give.

Grandma gives cupcakes to Sarah.

Take a look at this sentence and notice that the verb gave has  two complements — the noun cupcakes and the prepositional phrase to Sarah. But this verb give has another possible grammatical structure that means exactly the same thing.

Grandma gives Sarah cupcakes.

In this alternate structure, the verb also has two complements, but now they are both nouns. Sarah, which was the complement to the preposition in the other structure, is now the first complement, and cupcakes has become the second complement.

The fact that our mental grammar generates both these structures for this verb and its complements is called an alternation. There are other alternations in our mental lexicon, but this particular one is called the dative alternation, which comes from the Latin word for give. Most of the verbs that allow the dative alternation are verbs that have a meaning that’s related to giving.

Send and hand are additional examples:

She sent a letter to her grandmother. // She sent her grandmother a letter.

She handed a coffee to her friend. // She handed her friend a coffee.

Some verbs take complements that are entire sentences. Each of the following verbs has a complement that could stand alone as a sentence: hope, doubt, wonder, and ask.

Ann hopes that the Leafs will win.

Bev doubts that the Leafs can win.

Carla wondered if she should cancel her season’s tickets.

Divya asked whether Eva liked hockey.

Each of these sentences, or clauses, is embedded inside the larger sentence.  And each one is introduced by a word from the category of complementizers. The words that, if, and whether are called complementizers because they introduce complement clauses.

While the complement in each of these cases could be a sentence in its own right, in this case, it’s embedded inside a larger sentence — it’s the complement to the verb hopes.

Check Your Understanding


Adjectives appear in a couple of predictable positions. One is between the word the and a noun:

the red car

the clever students

the unusual song

the delicious meal

The other is following any of the forms of the verb be:

That car is red.

The students are clever.

The song is unusual.

The meal was delicious.

Many adjectives can be intensified with the words very or more:

very clever

more unusual

very delicious

And some adjectives (but not all) have comparative and superlative forms:

red – redder – reddest

smart – smarter – smartest

tall – taller – tallest

tasty – tastier – tastiest


The behavior of adverbs is a little more difficult to observe. Unlike adjectives, adverbs don’t have comparative or superlative forms, but, like adjectives, they can be intensified with very or more:

very quickly

very cleverly

more importantly

The above examples illustrate that many adverbs are derived by affixing -ly to an adjective. However, there are also many adverbs that are not derived this way, and there are also some common English words that have the -ly affix that aren’t adverbs, but adjectives, like friendly, lonely, lovely, so the affix is not a reliable clue. The syntactic distribution of adverbs is also a little slippery. Adverbs can precede or follow verbs to provide information about the verb:

The children sang beautifully.

The students complained loudly about the pop quiz.

They had just arrived when the fire alarm rang.

Samira tripped and nearly broke her wrist.

The visitors will arrive tomorrow.

And adverbs can precede adjectives or other adverbs to provide information about the adjective/adverb:

This meal is surprisingly tasty.

An extremely expensive car drove by.

The children finished their homework remarkably quickly.

Because their behavior is more variable than that of words in the other open-class categories, adverbs can be a challenge to identify. They are often confused with adjectives. Asking a few key questions can help you determine if a word is an adjective or an adverb.

Adjective or Adverb?

Ask the following questions about the word in question:

  • How? When? Where? If the word answers one of these questions, it’s an adverb.
  • What kind? Which one? How many? If the word answers one of these questions, it’s an adjective.

A Note on Compound Words

In our chapter on Morphology, we discussed the creation of new words. One common way to create a new word is through compounding. A compound word doesn’t really have a base or root that determines the meaning of the word. Instead, both pieces of a compound make a sizeable contribution to the meaning. For example, yoga pants are pants that you wear to do yoga, and emerald green is the particular color of green that emeralds are. So it doesn’t make sense to say that compounds have a root.

On the other hand, there is one part of a compound that has a special role, which we can see if we think about the categories of the words that make up a compound.

dry clean
stir fry
power wash

Each of the compound words above is made up of a different category of the word on the left plus a verb on the right. But in each case, the compound word is a verb. Even if both parts of a compound contribute to the meaning of the compound, it’s the head of a compound that determines its category. We say that English is a head-final language because in English the second part of the compound determines the category of the compound. Other languages are head-initial, with the head as the first element in a compound.

In many compounds, the head determines the category and also constrains the meaning of the compound. So dog food is a kind of food, not a kind of dog, and yoga pants are a kind of pants, not a variety of yoga. Compounds like this, where the meaning relationship between the head and the whole compound is obvious, are called endocentric. But in some compounds, the meaning relationship is not so transparent.  For example, a redhead is a person, not a kind of head; a nest egg is money that you’ve saved, not a kind of egg; a workout is not a particular kind of out; and Facebook is not a book at all! Compounds where the meaning of the head does not predict the meaning of the compound are said to be exocentric.

Check Your Understanding

Closed-Class Categories

Content words convey a lot of the meaning of a sentence. But not many sentences would be complete if they contained only nouns, verbs, or adjectives. There are also several smaller categories of words called closed-class categories because the language does not usually add new words to these categories. These categories don’t have many members, maybe only a few dozen, in contrast with the many thousands of words in the open-class categories. They’re the function words or non-lexical categories that do a lot of grammatical work in a sentence but don’t necessarily have obvious semantic content.


The category of determiners doesn’t have many members but its members occur very frequently in English.  The two little words the and a are the most recognizable members. Determiners most often appear before a noun, as in:

a student

an orange

the snake

the ideas

Any word that can appear in the same position as the counts as a determiner, like demonstratives:

those students

these oranges

that snake

this idea

Quantifiers and numerals also behave like determiners:

many students

twelve oranges

most snakes

several ideas

And the words that you might have encountered as “possessive adjectives” or “possessive pronouns” behave like determiners as well:

my sister

your idea

their car


The category of prepositions seems to have slightly more obvious semantic content than most other closed classes. Prepositions often represent relationships in space and time. They also have consistent syntactic distribution, usually appearing with a noun phrase immediately following them:

on the table

in the basket

around the block

through the centuries

near campus

after class

One way to visual prepositions is to think about where an object might be in relation to a box.

Prepositions Illustration--an owl in different positions in relation to a box.
Prepositions by AttaNatta licensed (CC BY 2.0).


A very small category of words that does an important job are the conjunctions. There are only seven conjunctions, and, or, nor, for, so, but, and yet. The job that conjunctions do is to join two words or phrases that belong to the same category:

oranges and lemons

brushed her teeth and went to bed

strong and fast

soup or salad

neither singing nor dancing

hated her roommate but loved her roommate’s sister

small but mighty

Complementizers (Part II)

You might have learned that words like because and although are a type of conjunction, but they don’t behave like and, or, but. Their behavior is more similar to a category of words we label as complementizers. Complementizers are function words that introduce a clause, which is a sentence embedded inside a larger sentence:

Sam told us that she loved baseball.

She hoped that the Blue Jays would win the World Series.

Leilani wondered whether it would rain that afternoon.

She asked her roommate if she had heard the forecast.

The roommate checked the forecast because she wanted to go for a run.

She decided to go running although a storm was forecast.

Mel washed the dishes while the cupcakes were in the oven.


Auxiliaries are what you might have called “helping verbs” when you first learned about grammar: they help a lexical verb by providing grammatical information about a verb’s tense or aspect, or other subtle elements of meaning.

Modal Auxiliaries

There are nine modal auxiliaries, which never change their form because they are never inflected: can, could, shall, should, will, would, may, might, and must.

Kieran can sing really well.

Laura could climb that rock wall.

We shall decide by drawing straws.

You should take a nap.

The guests will arrive soon.

Malik would like to read that book.

You may leave after you’ve finished the test.

The road might be slippery.

Drivers must obey all traffic laws.

Non-Modal Auxiliaries

The verbs have, be, and do sometimes behave like auxiliaries and sometimes like ordinary lexical verbs. Unlike the modal auxiliaries, have, be and do get inflected (had, has, having, am, is, are, was, were, been, being, did, done, doing), so, even when they are auxiliaries, they are non-modal. Their inflection is not a clue to whether they are auxiliaries or not, so we have to look at their behavior in the context of a sentence. If a sentence includes a lexical verb or main verb, then have, be or do in that sentence is likely to be an auxiliary, helping the lexical verb.  In the following examples, the auxiliary verbs are underlined and the lexical verbs (also known as main verbs) are bolded:

Arlene is writing a novel.

Beulah has arrived in Saskatoon.

Carmen is planning her vacation.

Doris did not buy any vegetables.

Evlien has been thinking about switching programs.

In addition to their auxiliary functions, have, be and do also have some lexical meaning of their own.  If there’s no other verb in the clause, then have, be, or do is probably the main verb of a clause. In these examples the lexical verbs are bolded:

Foster is proud of his sister.

Green vegetables are important for good health.

Harold has an idea for an app.

Ira did his homework before supper.

Javier had a big party.

If have, be or do serves as the lexical verb, then it might also have some auxiliaries helping out:

Foster has been proud of his sister.

Green vegetables might be important for good health.

Harold did have an idea for an app.

Ira could have been doing his homework before supper.

Javier is having a big party.

Notice that not every sentence has an auxiliary, but every sentence does have a lexical verb.

Check Your Understanding

Category Differences in the Brain


In the following paragraph, identify all the nouns, verbs, and adjectives:

“The main door of the school is on the side away from the town. The drive leading to it is long, cutting straight across between the tennis courts after it leaves the big wooden gates, then curving round the extreme edge of the gardens until, after a long, straight stretch up the slope, it ends in the courtyard by the front door. It takes about five minutes’ fast walking to get from the gates to the grateful seclusion of the court during which you become thoroughly self-conscious as you notice the eyes watching you from the windows. Once you reach the corner of the house you are safe.”

So far, you’ve learned how to categorize words according to their behavior, which categories are open to new members, and which categories are not. You’ve also learned that compounding is a very productive means of deriving new words in English by combining two words. While most compounds are endocentric and have a head that determines the meaning and category of the word, for exocentric compounds, the meaning of the compound drifts over time, leaving the compound without a head.


Phrases are syntactic units that consists of one or more words. They are intermediate constituents between words and clauses/sentences.

Word: dog

Phrase: off the dog (Words are connected together. Phrase could have a subject or a verb, but not both.)

Clause: when she washes off the dog  (A clause contains a subject and a verb, but is not a complete sentence.)

Sentence: She washes off the dog.  (Contains a subject and a verb and forms a complete sentence.)

The words of a phrase cohere together to form a single syntactic unit, which can be moved around and substituted by another word or phrase:

  1. The boys ran down the hill.
  2. Down the hill, the boys ran. (movement)
  3. They ran there. (substitution)

Phrases are formed out of the main lexical word classes: adjective, adverb, noun, preposition, and verb. The major phrase types thus include:

  • Adjectival Phrase (AP), e.g. very [premodifier = intensifier] proud [head = adjective] of you [postmodifier = prepositional phrase]
  • Adverbial Phrase (AdvP), e.g. too [premodifier = intensifier] carefully [head = adverb] for us [postmodifier = prepositional phrase]
  • Noun Phrase (NP), e.g. the [premodifier = determiner] book [head = noun] on the table [postmodifier = prepositional phrase]
  • Prepositional Phrase (PP), e.g. just [premodifier = adverb] over [head = preposition] the bridge [postmodifier = noun phrase]
  • Verb Phrase (VP), e.g. furiously [premodifier = adverb] hammered [head = verb] the door [postmodifier = noun phrase]  (VP), e.g. furiously [premodifier = adverb] hammered [head = verb] the door [postmodifier = noun phrase]

Phrases consist of heads and modifiers. The head is the central obligatory element (often a word) which determines the type of the phrase. Note that in the examples above, the head is surrounded by the premodifier and the postmodifier. However, a phrase doesn’t have to have both a pre- and a postmodifier.

Check Your Understanding

X-Bar Theory

Within each sentence, our mental grammar groups words together into phrases and phrases into sentences.

One theory of syntax is called X-bar theory. X-bar theory makes the claim that every single phrase in every single sentence in the mental grammar of every single human language has the same core organization. According to x-bar theory, every phrase has a head. The head is the terminal node of the phrase. Whatever category the head is determines the category of the phrase. So if the head is a Noun, then our phrase is a Noun Phrase, abbreviated NP. If the head is a verb (V) then the phrase is a verb phrase (VP). And likewise, if the head is a preposition (P), then the phrase is a preposition phrase (PP), and Adjective Phrases (AP) have Adjectives as their heads.

So the bottom-most level of this structure is called the head level, and the top level is called the phrase level. What about the middle level of the structure? Syntacticians love to give funny names to parts of the mental grammar, and this middle level of a phrase structure is called the bar level; that’s where the theory gets its name: X-bar theory.

So if every phrase in every sentence in every language has this structure, then it must be the case that every phrase has a head. But you’ll notice two pieces, the specifier and the compliment, or modifier. They’re optional — they might not necessarily be in every phrase. If they’re optional, that means that it should be possible to have a phrase that consists of just a single head — and if we observe some grammaticality judgments, we can think of phrases and even whole sentences that seem to contain a head and nothing else. We could have a noun phrase that consists of a single noun — Coffee? or Spiderman! We could have verb phrase that has nothing in it but a verb, like Stop!  or Run! Or an adjective phrase might consist of only a single adjective, like Nice… or Excellent!

But X-bar theory proposes that phrases can have more in them than just a head. A phrase might optionally have another phrase inside it. If there’s a phrase in that position, it’s called the complement. The most common kinds of head-complement relationship we see are a verb taking an object or a preposition taking an object. Let’s look at some examples.

Verb + Direct object: drank the coffee                                                                                                                                                 Preposition + Object of the Preposition: on campus

The other common place we see a head-complement relationship is between a determiner and a noun. In phrases like my sister, those shoes, and the weather, the determiner is a head that takes an NP complement.

The Sentence

The model of the mental grammar that we propose is quite simple: Words and features are stored in the mental lexicon, and the operation MERGE combines these words and features into organized, but simple structures, called sentences. In its simplest form, a sentence has a subject, a verb, and it makes complete sense on its own.

In this section, we learn how to observe the behavior of sentences to draw conclusions about how these structures are organized in our minds, and how to use the notation called tree diagrams to illustrate that organization.

Tree Diagrams

We’re about to start looking into how sentences are organized in our mental grammar. Before we do that, we need to be familiar with a particular kind of notation called a tree diagram. We’ll see that, within each sentence, words are grouped into phrases. Phrases can be grouped together to form other phrases and to form sentences. We use tree diagrams to depict this organization. They’re called tree diagrams because they have lots of branches; each of these little lines that join things in the diagram is a branch. Within a tree diagram, we can talk about the relationships between different parts of the tree.


Every place where branches join together is called a node. Each node corresponds to a set of words that act together as a unit called a constituent.

Each branch connects one node to another. The higher node is called the parent and the lower one is the child. A parent can have more than one child, but each child has only one parent. And, as you might expect, if two child nodes have the same parent, then we say that they’re siblings to each other. Most linguistics textbooks call these nodes “mother, daughter, and sister” nodes.

If a node has no children, we call it a terminal node.

Having this vocabulary for tree diagrams will allow us to talk about the syntactic relationships between the parts of sentences in our mental grammar.


We’ve started to use tree diagrams to represent how phrases are organized in our mental grammar. And we’re using the tree diagram notation to represent every single phrase as having X-bar structure. This unit shows some of the linguistic evidence that phrases have some reality in the mental grammar.

When we draw a tree diagram, we’re making a claim about how a sentence or phrase is organized in our mind. Every time we draw two or more branches coming together at a node, we’re making the claim that the node corresponds to a unit. In other words, all the daughters of that node behave together as a unit. Some of these nodes are at the phrase level, and some of them are at the bar-level.  The more generic term for a group of words that act together to form a unit is a constituent.

So what’s our evidence that constituents exist in our minds? Within a given sentence, how can we tell if a given string of words acts as a unit? Here again is where we rely on observing our grammaticality judgments, using a few simple tools.

Replacement Test

Here’s a simple sentence:

The students saw their friends after class.

Let’s consider the string of words their friends. You probably have an instinct that this is a noun phrase. But if you’re going to claim that it’s a constituent, it would be nice to have some evidence for that claim. One piece of evidence is that we can replace this set of words. Take the pronoun them and replace the string of words we’re investigating:

The students saw their friends after class.

The students saw them after class.

Then we ask ourselves whether the resulting sentence is grammatical. Replacing their friends with them does indeed leave us with a grammatical sentence, which is one piece of evidence that their friends is a constituent.Let’s test another chunk of this sentence. Let’s try the string of words after class. If we replace that set of words with the word then:

The students saw their friends after class.

The students saw their friends then.

And when we observe our grammaticality judgment, it turns out that this replacement is also grammatical. That’s some evidence that words after class behave together as a constituent in this sentence.We can do the same thing with the string the students. Replace that string with the pronoun they:

The students saw their friends after class.

They saw their friends after class.

And observe our grammaticality judgment, and we find evidence that the students is a constituent as well. What happens if we try to replace a string of words that isn’t a constituent?

The students saw their friends after class.

*The they friends after class.

*The did friends after class.

*The then friends after class.

*The them friends after class.

We can try lots of replacements, but when we ask ourselves whether the result is grammatical, the answer is No. There doesn’t seem to be anything that can replace the string of words students saw their. The fact that nothing can replace that string of words suggests that students saw their is not a constituent in this sentence. At this point, you’re probably wondering how you know what you can use as a replacement. Here are some handy tips:

  • Noun Phrases can be replaced with Pronouns (it, them, they).
  • Verb Phrases can be replaced with do or do so (or did, does, doing).
  • Some Preposition Phrases (but not all) can be replaced with then or there.
  • Adjective Phrases can be replaced with something that you know to be an adjective, such as happy.

Let’s see how this replacement tool works for a verb phrase. We’ll go back to our sentence and look for the verb, saw. Let’s test this set of words: saw their friends. Since saw is the past tense of see, we’ll try replacing it with did, the past tense of do, and observe our grammaticality judgment.

The students saw their friends after class.
The students did after class.

This replacement is grammatical, so that provides us with some evidence that the set of words saw their friends is indeed a constituent.

You can use this evidence as you’re drawing trees. If you can’t quite figure out which groups of words go together into certain phrases, you can try replacing different chunks of the sentence. The parts that allow themselves to be replaced, that is, the parts that can be replaced and still leave a grammatical sentence are constituents, and those parts will be joined under one node.

You can also use this evidence when you’re trying to figure out what category a certain phrase is: If you can replace it with a pronoun, then you’ve got a noun phrase and you can look for the noun as the head. If you can replace it with do or do so, then you’ve got a verb phrase which will have a verb as its head. Then and there are a little less reliable because they sometimes replace PPs or APs, but you’ll be able to tell the difference between prepositions and adjectives because prepositions usually have complements and adjectives don’t.

Movement Test

Replacement is not the only tool we have for checking if a set of words is a constituent. Some constituents can be moved to somewhere else in the sentence without changing its meaning or its grammaticality. Preposition Phrases are especially good at being moved. Look at this sentence:

Nimra bought a top from that strange little shop.

Let’s start by targeting the last string of words by moving it to the beginning. Move the string of words then ask yourself whether the resulting sentence is grammatical.

Nimra bought a top from that strange little shop.

From that strange little shop Nimra bought a top.

Yes, it is. Standing here in isolation, the sentence might sound a little unnatural, but we can imagine a context where it would be fine, such as, “At the department store, she bought socks, at the pharmacy she bought some toothpaste, and at that strange little shop, she bought a top.” On the other hand, if we target a smaller string of words:

Nimra bought a top from that strange little shop.

*From that strange, Nimra bought a top little shop.

If we try to move that string to the beginning of the sentence, the result is a total disaster. The fact that the resulting sentence is totally ungrammatical gives us evidence that the string of words from that strange is not a constituent in this sentence.

Cleft Test

There’s a version of the movement tool that can be useful for other kinds of phrases. It’s called Clefting. A cleft is a kind of sentence that has the form:

It was ____ that …

To use the cleft test, we take the string of words that we’re investigating and put it after the words It was, then leave the remaining parts of the sentence to follow the word that. Let’s try it for the phrases we’ve already shown to be constituents.

Nimra bought a top from that strange little shop.

It was from that strange little shop that Nimra bought a top.

The students saw their friends after class.

It was their friends that the students saw after class.

It was after class that the students saw their friends.

And let’s try the cleft test on another new sentence.

Rhea’s sister baked these delicious cookies.

It was these delicious cookies that Rhea’s sister baked.

It was Rhea’s sister that baked these delicious cookies.

The cleft test shows us that the string of words these delicious cookies are a constituent, and that the words Rhea’s sister are a constituent. But look what happens if we apply the cleft test to another string of words:

Rhea’s sister baked these delicious cookies.

*It was sister baked that Rhea’s these delicious cookies.

Rhea’s sister baked these delicious cookies.

*It was these delicious that Rhea’s sister baked cookies.

Rhea’s sister baked these delicious cookies.

*It was cookies that Rhea’s sister baked these delicious.

All of these applications of the cleft test result in totally ungrammatical sentences, which gives us evidence that those underlined strings of words are not constituents in this sentence.

Question Test

If a string of words is a constituent, it’s usually grammatical for it to stand alone as the answer to a question based on the sentence.

Rhea’s sister baked these delicious cookies.

  • What did Rhea’s sister bake? These delicious cookies.
  • Who baked these delicious cookies? Rhea’s sister.

The answer-to-questions test can also help us identify a verb phrase using do-replacement:

  • Who baked these delicious cookies? Rhea’s sister did.

Notice that in the answer, “Rhea’s sister did”, the word did automatically replaces the verb phrase baked these delicious cookies. Again, if a string of words is not a constituent, then it is unlikely to be grammatical as the answer to a question. In fact, it’s difficult to even form the right kind of question:

What did Rhea’s sister bake cookies? *these delicious

Who of Rhea’s these delicious cookies? *sister baked

Remember that tree diagrams are a notation that linguists use to depict how phrases and sentences are organized in our mental grammar. We can’t observe mental grammar, so observing how words behave is how we make inferences about the mental grammar.

These four tests are tools that we have for observing how words behave in sentences. If we discover a string of words that passes these tests, then we know that the phrase is a constituent, and therefore there should be one node that is the mother to that entire string of words in our tree diagram. Not every constituent will pass every test, but if you’ve found that it passes two of the four tests, then you can be confident that the string is actually a constituent. When you’re drawing trees, use these tests as a check every time you draw a mother node.

Check Your Understanding

Syntactic Functions

Constituents can be classified not only based on their form (internal structure) but also according to their function, i.e. the role they play in the clauses and sentences of which they are a part.The most general traditional functional distinction is between subject and predicate. The subject is often defined as the constituent specifying the topic of the sentence, whereas the predicate is that which is asserted about the subject. By reversing the order of subject and predicate, statements can be turned into questions.


Central to syntactic analysis and theory is the notion of grammar. In theoretical linguistics, grammars are theory-based coherent systems of rules and principles which model a speaker’s knowledge of language.

There is a great deal of confusion about the term ‘grammar’. Most people associate with it a book written about a language. In fact, there are various manifestations of this traditional term:

  • Prescriptive grammar
  • Descriptive grammar
  • Reference grammar

In theoretical linguistics, grammars are theory-based coherent systems of rules and principles which model a speaker’s knowledge of language. These formal grammars combine insights from all branches of linguistics, with syntax in the center. The most important formal grammar model is generative grammar.


Prescriptive Grammar

Most people first encounter grammar when they study their own or a second language at school. There, they experience grammar as a collection of rules concerning what counts as ‘correct’ and ‘incorrect’ language use.

This kind of grammar is called normative, or prescriptive, because it seeks to establish norms of ‘correct’ grammatical usage. Prescriptive grammars lay down rules as to how words and sentences are to be put together in a language so that the speaker or writer will be perceived as having “good grammar”. This makes them similar to books on etiquette, which recommend certain types of conduct.

Examples of prescriptive rules in English include:

  • Do not use ain’t.
  • Do not use seen as the past tense of see. (e.g. I seen her at the party last night).
  • Do not start a sentence with a conjunction.
  • Do not use contractions (such as can’t, don’t, won’t)
  • Do not use sentence fragments (e.g. Who did that? -> My brother).
  • Do not end a sentence with a preposition.
  • Do not use split infinitives. (To boldly go…)
  • Do not use who, but whom, as the object of a verb or preposition.

Descriptive Grammar

Rules of prescriptive grammar state how people ought to speak and write. Another approach, which became popular in the early 20th century, is to write grammars of rules that do not prescribe, but rather describe how people actually speak, whether or not they are speaking ‘correctly.’

These descriptive rules have the status of scientific observations, and they are intended as generalizations about the way language is used in fact. A descriptive grammar thus seeks to give a precise account of the actual grammatical state of a language, which may also shed light on how the human language capacity as such works.

Linguistics, the scientific study of language, is hence essentially descriptive in character. This was first emphasized by Ferdinand de Saussure.

When linguists study a language to develop a grammar for it, they adopt a scientific method that involves iterating through the following steps:

  1. Gather and observe data from various sources (e.g. corpora).
  2. Make generalizations about patterns in the data (e.g. “In simple English declarative sentences, the subject precedes the verb.”)
  3. Develop hypotheses (rules, principles) that account for these generalizations.
  4. Test the hypotheses against more data and (if necessary)refine or revise them.


Test your own knowledge! Are the given sentences grammatical or ungrammatical?

Take the Quiz

Reference Grammar

One special type of descriptive grammar is the reference grammar. Designed as a book for reference rather than for teaching, it aims at a complete description of all grammatical aspects of a language. Hence, a reference grammar is similar to a dictionary (the reference book of all words).

The best known reference grammar of the English language is the one written under the supervision of Randolph Quirk. It has almost 1800 pages and includes, apart from the syntactic description of English, some aspects of morphology as well as of phonology.

Formal Grammar

A formal grammar is a systematic and explicit description of the structure of a particular language or of human language in general, which is based on a specific linguistic theory. It is a model of the linguistic knowledge developed in the minds of the speakers of a language.

Traditionally, the domain of formal grammar was word and sentence formation (i.e. morphology and syntax). In contrast, linguistics today commonly takes grammar to encapsulate the whole range of knowledge possessed by speakers (phonological, morphological, syntactical, and semantic knowledge).

Various kinds of formal grammar with different underlying theoretical frameworks have been developed, among them:

  • Dependency grammar
  • Functional grammar
  • Construction Grammar

The most prominent formal grammar model, however, is generative grammar. This theory of language is closely associated with the American linguist Noam Chomsky and has influenced linguistic thought to a high degree.

Acquisition of Syntax

Babies start to learn the phonology of their first language very early — as soon as they’re born (and maybe even earlier than that!). What about syntax? What do babies and young children know about the syntax components of their grammar? And how can we tell?

Here is a video explanation that shows how children develop syntax–the ability to speak in sentences.

Interestingly, Dr. Laura Ann Petitto discovered that, whether a child is learning language through hearing speech sounds or through sign language, they develop language at the same rate. Dr. Petitto’s Research

On average, children start to speak their first word around age one, and they start to combine two or more words some time after that, by about age one and a half. But if you’ve ever spent any time with young children, you know that they can understand a great deal more than they can say! Their comprehension is often much more advanced than their ability to produce spoken or signed words. But comprehension is much harder to observe. How can we tell what babies and toddlers understand about language?

One simple technique is called preferential looking. In this kind of experiment, researchers use a large screen or television. The baby or toddler sits strapped into a booster seat, facing the screen. The screen is split so that two different pictures appear, one on each side of the screen. While the pictures or are on the screen, a recorded voice speaks a sentence, maybe something like, “Look! Can you find the foot?” The idea is that if the baby understands the word foot, they’re going to look at the picture of the foot, not the picture of the banana. The researchers keep track of the direction of the baby’s head-turn, or they use eye-tracking to measure the baby’s eye movements. This kind of experiment has shown that babies pretty reliably look at the named object by about ten months, and even as young as six months, they’re looking at the named object more often than chance would predict. So at the age of six months, babies are already beginning to link up word forms with their meanings. What that means is that we can use this same preferential looking technique to figure out what kids know about syntax.

Instead of a picture of a single item, we could use the split screen to display two similar scenes and use language to describe one of the two scenes. If children look towards the matching scene, does that mean they know something about syntax? Or are they just paying attention to the word meanings?

Do you remember the idea of compositionality? It says that syntax matters for sentence meanings — the meaning of a sentence comes not just from adding together the meanings of the words, but also from the way those words are combined, that is, from the syntax. Children as young as 15 months, just a little over one year, look more often towards the correct image or video when given a description of a scene. That suggests that they’re not just adding together the meanings of the words in the sentence, but that they’re also sensitive to the way those words are combined, to the syntax, because that’s what distinguishes the kid chasing the woman from the woman chasing the kid.

So kids who are just a little older than one are already sensitive to syntactic constituent structure and its relation to meaning. What else do young children know about syntax? Some experiments with young children don’t involve screens, but actual toy items. In one experiment, researchers introduced 14-month-old children to novel, made-up words, that the children would not already be familiar with.

The experimenter presented small toys to the child and said, “These are blickets. This one is a blicket and this one is a blicket.” So the child had a couple examples of what a blicket is. Then the experimenter presented two new toys, one of which was from the same category as the earlier ones — in this case, the category of animals — but was a different color, and the other of which was the same color, but from a different category. When the experimenter asks, “Can you give me the blicket?” if the child reaches for the new toy of the same category, that tells us they’ve figured that blicket means animal. But if they reach for the same color, they’ve concluded that blicket means pink thing.

The 14-month-olds reached for the new animal of a different color more often than they reached for the toy that matched in color. But the pattern was reversed for children who heard a different syntactic frame. If the toys had been introduced with the new word in an adjective position, “These are blickish. This one is blickish and this one is blickish,” then when the experimenter asked, “Can you give me the blickish one?“, the children were much more likely to choose the one that matched in color.

These results indicate that when one-year-olds hear a new word in a noun position, they conclude that it has a noun-like meaning, and refers to a thing or a category of things. But if it’s in adjective position, then its meaning is probably something more like an attribute or property. In short, one-year-olds seem to be sensitive to the differences between syntactic categories.

There’s so much learning happening in that second year. Kids are learning new words very rapidly, and learning how words pattern in the morphological and syntactic behavior. In fact, by the time they turn two, kids are sensitive to verb subcategories too!

In one split-screen experiment, when experimenters presented the novel verb mooping in a transitive frame, like “The lady is mooping my brother,” then two-year-olds looked more often to the scene where one participant is doing something to the other, like pushing. But when the novel verb appeared in an intransitive frame, like “The lady and my brother are mooping,” then the children looked more often to the scene where the two participants are doing the same activity together, like waving. This suggests that, by age two, children are sensitive not only to syntactic categories, but also to subcategories!

An example of these kinds of tests come from a researcher in psycholinguistics, Jean Berko Gleason, created the Wug Test, in which a child is shown pictures with nonsense names and then prompted to complete statements about them, and used it to demonstrate that even young children possess implicit knowledge of the rules of language. In the following video, Gleason gives the Wug Test to Laura Wilcox:


So to go back to the question we started with, “What do kids know about syntax?” It turns out the answer is that, even before children start combining words to make phrases in their own speech or signing, they already know quite a lot about how words combine in the grammar.


In this chapter, we’ve seen that we can group words into categories according to how they behave. We know that words within a particular syntactic category behave similarly to the other words in that category. They’re similar in their inflectional morphology and in their syntactic distribution, that is, what positions they can occupy in a sentence. That’s linguistic evidence that syntactic categories are real.

Interestingly, there’s also neurolinguistic evidence that our brains respond differently to words from different categories. Lorraine Tyler and her colleagues used functional magnetic resonance imaging (fMRI) to measure blood flow to different regions of the brain. The idea behind fMRI is that brain activity consumes oxygen, and when a particular area of the brain is active, then more blood flows there to bring it more oxygen.

The researchers asked people to do an easy task. They showed them lists of three words and asked them to decide if the third word, the one in all caps, was related to the first two. So in this example, sparrows, thrushes, and wrens are all kinds of birds, so the participants would respond Yes. In this next example, hammer, wrench, banana, the first two are tools but the third one is a fruit, so it’s not related to the first two, so the participants would answer No.

What they discovered is that, in typical brains, a simple task with verbs involves greater brain activity than the same task with nouns. All this suggests that our brains treat words differently depending on what category they’re in. Or in other words, different syntactic categories exist not just in language, but also in the brain!

British vs American English

Because our focus in this text is on the English spoken in the United States, let’s take a moment to explore how American English differs from British English syntactically. While you might associate British English with a different accent, there are actually some significant syntactic differences in the mental grammar of British and American English.

  • Collective Nouns: In British English, collective nouns can take either singular or plural verb forms, while in American English collective nouns are almost always singular.
  • Verbal Auxiliaries:
    • Shall is much more commonly used by the British than by modern-day Americans, who generally prefer will. However, shall is still common in American legal documents.
    • Shan’t is typically regarded by Americans as a stereotypical British construction; in AmE, it is almost always replaced by won’t or am/are/is not going to or their contractions.
    • In both British and American grammar, would and should have different meanings. However, in British grammar, it is also possible for should and would to have the same meaning, with a distinction only in terms of formality (should simply being more formal than would).
    • Use of “do” as a pro-predicate is almost exclusively British usage.
      • Example: “Did Frank love it?” — “He must have done.”

      The AmE response would be “He must have,” omitting the form of “do”.

  • Where a statement of intention involves two separate activities, speakers of BrE often use “to go and” plus the infinitive while it is also acceptable for speakers of AmE to use “to go” plus infinitive. ie “I’ll go and take a bath” vs “I’ll go take a bath.”
  • Use of prepositions before days denoted by a single word: The British say She resigned on Thursday, but Americans often say She resigned Thursday, although both forms are common in American usage.
  • The adverb well may be used in colloquial BrE only with the meaning “very” to modify adjectives. For example, “The film was well good.”

These are just a few of the interesting syntactical differences between British and American English.


From the time we first begin to learn language as babies, our brains begin to adapt to the syntax of the language that we are learning. Even when we are technically speaking the same language, as in British and American English, subtle differences in syntax can exist and become part of the way we understand language, even from infancy. As we continue to explore American English, keep this in mind!



This chapter is licensed CC-BY-SA.

Content in this chapter has been adapted from the following:

VLC206-Form, Function & Grammar by Jürgen Handke, Peter Franke, Linguistic Engineering Team under CC BY 4.0

Essentials of Linguistics by Catherine Anderson licensed CC BY SA 4.0.

Jean Burko Gleason” available under the CC BY SA 3.0.

British vs American English licensed CC-BY-SA-4.0.

Media Attributions

  • Prepositions


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More than Words Copyright © 2022 by Dr. Karen Palmer is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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