C. George Boeree

The syntax of a language is the set of rules that language uses to combine words and morphemes to create sentences. For example, in some languages adjectives come before the noun, and in others after the noun. Some languages use prepositions, others use postpositions. In some, the verb is at the beginning of the sentence, in others it is at the end, and in others still it is somewhere in the middle. But rules such as these only scrape the surface!

We start with a basic classification of words, the parts of speech (aka lexical categories): Nouns, verbs, adjectives, adverbs, prepositions, and so forth. These then combine into phrases.

A noun phrase consists of a noun and all its modifiers - i.e. determinants, adjectives, and any clauses or prepositional phrases that modify the noun. (We will get to clauses in a bit.) Traditionally, the noun is called the head of the noun phrase,  because it determines the syntactic function of the phrase - that is, the phrase acts as if it were a noun.  Examples: "Bob", "the cat in the hat", "a whole other problem", "the man who came to dinner", etc.

Some linguists use the term argument to refer to noun phrases, especially to the subject and the object in a sentence.

A verb phrase consists of a verb and all its modifiers - i.e. adverbs, auxiliary verbs, prepositional phrases, and adverbial clauses.  Most linguists would also include noun phrases such as the object and complements, in the definition of a verb phrase. The verb is, of course, the head of the verb phrase. Examples: "stop!", "walk carefully", "will soon greatly regret", "came in the middle of the night", "hurt his pride", "put out the cat", etc.

Just to make things more complicated, some linguists use the term predicate, which overlaps with "verb phrase".

A prepositional phrase consists of a preposition (which is the head of the prepositional phrase, of course) and a noun phrase. If the language uses postpositions, we call it a postpositional phrase. Together, they are called adpositional phrases.

Finally, there are adjectival phrases and adverbial phrases. If you say "that man is full of bull", "full of bull" (an adjective "full" followed by a prepositional phrase "of bull") is an adjective phrase. Similarly, in "he walked very slowly", "very slowly" (an adverb "slowly" preceded by a modifier "very") is an adverbial phrase.

Complements are words or phrases (and sometimes even clauses) that tell us more about a noun or a noun phrase, but do so by means of a verb. For example, in the sentence "he looks sick", "sick" modifies "he", but uses the verb "looks" to make the connection.  In "we painted the town red", "red" modifies "town" by means of the verb "painted". In "I am in a good mood", "in a good mood" modifies "I", by means of the verb "am".

As you can see by the examples, the most common verb used to link a complement to a noun is the verb "to be" - known in linguistics as a copula. Other copulas include "become", "seems", "turned", "appears", etc. The copula with a noun complement ("he is the king") is sometimes called a predicate nominal.  The copula with an adjective ("he is stupid") is sometimes called a predicate adjective.


A clause is a set of words that includes at least a verb and probably a subject noun. In some cases and languages, the subject may be implied. A sentence is actually a clause.  But a sentence can have more than one clause: There may be a main clause (or independent clause) and one or more subordinate clauses.  This kind of sentence is called a complex sentence.

Subordinate clauses come in several forms:

An adverbial clause is one which modifies the main clause in the manner of an adverb. They are typically introduced by subordinating conjunctions, which are, in English at least, the same as question words. For example:

I am not afraid of the dog, because it is very small.
If they lose weight too quickly, they will regain it afterwards.
I'm running so that the rhinos don't catch me.
He wrote when his mother asked.
He is happy where he lives.
I wasn't allowed to do things as I wanted.

An adjectival clause (or relative clause) is one that modifies a noun phrase. They typically are introduced by a relative pronoun, which serves as la subject of the clause. For example:

The man who lived here went to New York.
The car that came from Italy is very fast.
The apple which fell from my bag is now inedible.

The noun phrase can also be the object of the adjectival clause, or even the object of a preposition. Notice how, in English, we often drop the relative pronoun:

The woman (whom) I love comes from France.
The robot (that) I built doesn't work.
The woman, of whom we speak, works at my office.
Your book, in which I wrote her name, is on the table.

Finally, adjectival clauses are sometimes introduced by a relative adverb. Notice how, if you drop the noun, the clause becomes an adverbial clause:

I eat in Paris, where I live. (I eat where I live.)
He will visit in July, when the weather is good. (He will visit when the weather is good.)
That's the reason why Juan left. (That's the reason Juan left; That's why Juan left.)

A noun clause is one which plays the part of a noun in the larger sentence.  They too are typically introduced by relative pronouns or adverbs. If you want to figure out if you are looking at a noun clause, substitute him, her, it, or them for relative word. If you still have a meaningful sentence, then the clause was a noun clause. Notice also that, if you were to add a noun before the relative pronoun or adverb, you change the clause into an adjectival clause:

I see where you are. (I see the place where you are.)
When I will depart, I just don't know. (The time when I will depart, I just don't know.)
I know who said that. (I know the person who said that.)
I heard what you said. (I heard the thing you said.)
I can guess which he's reading. (I can guess which book he's reading.)

There are also noun clauses that are introduced by a subordinating conjunction such as the English "that":

I know that you don't like me.
She thinks (that) I'm silly.
They were surprised that he could jump that high.

Finally, a sentence can have two or more main (independent) clauses, joined by coordinating conjuntions. This kind of sentence is called a compound sentence:

I want to sing and I want to dance, but I have no talent.
Either he goes or I go.

Kinds of sentences

Most sentences are simple statements about the world or one's thoughts or feelings. These are called declarative sentences or just declarations. Most of the examples above a declarations.

are a kind of sentence that often involves complications of syntax in many languages. First, there are three kinds of questions. The first is the yes/no question. In these examples, you can see some of the syntactical techniques we use in English, such adding "do", moving the verb, or adding a tag such as "did you?"

Are you going to town?
Do they like it?
You didn't forget, did you?

There are also choice questions, which require a simple answer selected from the options given in the question:

Do you want broccoli or cauliflower?
Should I wear my jacket or a sweater?

The final kind is the wh- question, which involves the use of interrogative words (pronouns and adverbs) such as who, what, which, when, where, how, how many, and why. These require a fuller answer:

Why are you going to town?
How many are going with you?
And when do you leave?

Another kind of sentence is the command. The usual kind involves the speaker telling someone else to do something, such as "pick up your clothes!". Commands may also involve exhortations to one's own group, such as in the sentence "let's go!" And commands can also blend into the question category of sentences when we make polite requests, such as "would you pass the tea, please?"

One common syntactic "trick" for commands is to drop the subject, which is understood.  In English, most commands are directed at "you", so why bother including that pronoun?  If the command is directed at "us", then we use "let us" before the verb. Other languages have other techniques, of course.

The last kind of sentence is the exclamation. This kind of sentence expresses an emotional reaction to the situation.  For example, "what a lovely day!" tells us not only that it's a lovely day, but that I am exceedingly pleased by it. Notice that this particular sentence does not contain a verb, and that is quite common in exclamations. In fact, many exclamations are single words: "crap!" "oy!" "weeee!" "hello!" etc.  These are called word-sentences, and the words are called sentence words.

Phrase structure

Traditionally, linguists have several ways of diagramming the structure of a sentence.  One way is called phrase structure rules.  For example:

S -> NP VP
"A sentence is made up of a noun phrase and a verb phrase."
NP -> (Det) (AP) N (PP)
 "A noun phrase is composed of a noun plus optional determinantes, adjective phrases, and prepositional phrases."
VP  -> (Aux) V (NP) (PP) (AdvP)
"A verb phrase is composed of a verb plus optional auxiliary verbs, object noun phrases, prepositional phrases, and adverbial phrases."
AP -> (AdvP) A
"An adjective phrase is composed of an adjective and optional adverbial phrases."
PP -> Prep NP
"A prepositional phrase is composed of a preposition and a noun phrase."
AdvP -> (Adv) Adv
"An adverbial phrase is composed of an adverb and optional modifying adverbs."

These phrase structure rules can then be used to construct phrase trees.  Here's one of the most famous of these trees, concerning the famous linguist Chomsky's famous meaningless (but grammatical!) sentence "Colorless green ideas sleep furiously":

In Chomsky's original theory, each language has a basic syntax - set of rules for the construction of basic sentences - and another set of rules for altering those basic sentences to fit particular uses. That second set of rules are called transformation rules, and they look a lot like the phrase structure rules we just discussed.  For example, in English, we can take a basic sentence like "He likes apples" and turn it into the question "does he like apples?" via certain rules. In English, we would take the auxiliary verb and move it to the beginning of the sentence. This is called subject-auxiliary reversal. If there is no auxiliary verb, we have to insert a "dummy" verb "do" and move that to the beginning of the sentence:

N1 V N2 => N1 Aux V N2
"Insert the auxiliary do in front of the verb."
N1 Aux V N2 => Aux N1 V N2
"Move the auxiliary do  to the front of the sentence."

To turn that same sentence into "what does he like?" we start with "he likes X". We perform the subject-auxiliary reversal to turn it into a question ("he does like X" followed by "does he like X?"). We substitute the interrogative pronoun "what" for X, then move it to the front of the sentence ("does he like what?" followed by "what does he like?"). This last step is called wh- movement:

N1 V N2 => N1 Aux V N2
"Add the auxiliary do in front of the verb."
N1 Aux V N2 => Aux N1 V N2
"Move the auxiliary do to the front of the sentence."
Aux N1 V N2 > Aux N1 V Pn
"Place the interrogative pronoun what  where the answer would be."
Aux N1 V Pn > Pn Aux N1 V
"Move the interrogative pronoun what  to the front of the sentence."

For obvious reasons, this theory was called transformational grammar. Since Chomsky, theories of syntax have been either (1) elaborations of transformational grammar or (2) alternatives to transformational grammar.

One interesting offshoot of Chomsky's original theories is the idea of universal grammar. This is the idea that all language begins with a single deep structure, the structure from which the transformations proceed. Furthermore, that deep structure is innate to the human brain in the form of a language acquisition device or LAD. The fact that other intelligent animals, such as the great apes, whales, dolphins, and elephants don't have anything close to the language capabilities of humans is said to be because they lack this evolutionary development. On the other hand, nothing quite as fully organized as the hypothetical LAD has been found in the human brain.

One family of alternative theories is called construction grammar (or CxG), which is strongly linked to developments in cognitive and cognitive developmental psychology. The basic idea here is that each language has a number of constructions a bit like Piaget's schemas. In fact, it postulates a whole taxonomy of these constructions - one for yes-no questions, one for simple commands, one for talking about how you feel about something, etc. etc. etc. So, instead of learning a list of transformations, we learn a list of constructions.  At the same time, when you learn a word, you also learn the kinds of constructions that word can fit in, in very much the same way that you learn implicitly that "cat" is a noun which therefore can be modified by adjectives and be the subject or object of a verb, and so on.  As a psychologist, I find construction grammar more appealing than transformational grammar.

© Copyright 2010, C. George Boeree