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Phrase Structure

Kyle Johnson

Syntax is the study of the arrangement of words into phrases and sentences. It

attempts to describe at least two aspects of this phenomena. First, it describes

which arrangements of words are grammatical, i.e. the well-formed ones. So it

is concerned with characterizing the contrast below:

() a. e woman le town.

b. * e le woman town.

(We use the convention of placing a “*” before strings of words that are not

grammatical.) And second, it describes the relationship between the meaning

that some particular group of words has and the arrangement of those words.

So, for example, the actions carried out by Mary and Mark in the following are

dierent, and this dierence corresponds to the dierent position that these

two words occupy in the sentence.

() a. Mary kissed Mark.

b. Mark kissed Mary.

Let’s begin with the rst of these goals of syntax, the grammatical arrange-

ments of words. At the bare minimum, we can observe that the linear order

of words in English is important; we must nd a means for describing which

ordering of words is well-formed and which not. e simplest means of do-

ing this is not available, i.e. we cannot merely list all the possible orderings

of words. at is, we do not have stored in our heads a long list of possiblesentences. e reason for this is simple: when we learn a new word, we know

where that word may be positioned with respect to other words. For example,

let me teach you a new word: stram. is is the name we shall give to a hair

that grows out of one’s ear. Now that you know that word, you also know that

the sentences below have the grammaticality values shown.

() a. at stram seems too short.

b. * Stram that short too seems.

is fact shows that we cannot encode our knowledge of arrangements of

words in terms of those words themselves. Instead we may make reference

to the “categories” (or “parts of speech”) that those words belong to. is willcorrectly account for the fact that once we know that a word is a noun, we

know automatically where it may fall in a sentence.

Perhaps, then, we store in our heads all the grammatical arrangements of

categories. is too cannot be correct; but for a more subtle reason. As the

following examples illustrate, sentences may be of indenite length.



2 Kyle Johnson

() a. Mary likes Mark.

b. John said that Mary likes Mark.

c. Sally believes that John said that Mary likes Mary.

d. Sandy thought Sally believes that John said that Mary likes

Mary.

Now it’s clear that a sentence of English cannot be innitely long. But we need

to determine whether this is a fact about our knowledge of the arrangement of

words. at is, we need to gure out whether our knowledge of syntax allows

innitely long sentences or not. If our knowledge of syntax does not allow

innitely long sentences, then our model of this knowledge — the grammar

we write — will have to reect this fact. But this means in essence that we

are going to have to decide at which point to terminate the expansion begun

above. is termination point would have to be arbitrarily chosen, and this

points to the inadequacy of supposing that our knowledge of syntax does

not encompass innite strings of words. In fact, the common conclusion

from these observations is that the failure of our ability to utter innitely longstrings does not reect some fact about our knowledge of syntax, but rather

some aspect of our abilities in general. In particular, our life-span, or perhaps

our limited memories or our good common sense, prevent us from uttering

such things. Our knowledge of syntax does not. is distinction is described

by saying that our linguistic “competence” is separate from our linguistic

“performance.”

But if our knowledge of which strings are grammatical and which aren’t

includes knowledge about innitely long strings, then we cannot possibly have

such a list in our heads. Our brains are of nite size and therefore cannot hold

things of innite length. Hence we must nd another means for representing

our knowledge of the well-formed strings of words. A list is wrong. eremust be some other way in which we recognize a string of words as a gram-

matical arrangement. ere must be some way this knowledge is encoded

in our minds that is nite, but still allows us to make a judgement about an

innite number of possible strings.

We are going to set aside the solution to this problem for awhile, and

discuss some other aspects of our knowledge of syntax. We shall encounter

other problems whose solution will solve the problem just discussed.

Consider the relationship between the following two sentences.

() a. Mary has le.

b. Has Mary le?

We know that these sentences are “related” in the following sense: they both

mean the same thing, save that one is a question, the other a statement. More

particularly, (a) is uttered when the situation described by Mary has le is

something the speaker wishes to assert. One would use this sentence, for

instance, to convey the belief that the situation (a) describes holds. We call



Phrase Structure 3

such sentences “declaratives.” By contrast, (b) is uttered when the speaker

wishes to determine whether the situation described by Mary has le actually

obtains. We call sentences of this sort “Yes/No Questions.” e important

point is that the situation both of these sentences describe is precisely the

same. e only dierence is whether the speaker is asserting that the situation

holds or seeking conrmation of it. is element of meaning is indicated by word-order. is is the fact that we need to capture. We need to fashion a

theory that causes the words of these sentences to combine to describe the

same situation, and correlate the dierence in their word order with whether

or not the sentence is a question or a declarative. is points back to the

second goal of syntax: to account for the relation between the arrangements

of words and their meanings. What we need to do in the case at hand is nd

a way of relating the word order dierences in () to the dierence in their

meaning.

e standard way of describing the relation between these sentences is to

suppose that one is derived by a rule from the other. at is, one sentence

is transformed into the other. In particular, we suppose that the question is“made of” the statement plus the application of some transformation that

moves around the constituents of the sentence to form the Verb-Subject word

order. We don’t know yet how to characterize our knowledge that Mary has

le means what it means and is a grammatical string of words (that’s what we

le unnished above), but let us suppose for this discussion that this aspect of

our knowledge is given. So we begin with Mary has le , and now concentrate

on the rule that yields Has Mary le? .

It appears on the face of it that this rule interchanges the rst two words.

But this is not what the rule does, as the following pair of sentences indicates.

() a. e woman has le.

b. * Woman the has le?

Perhaps what we should say, then, is that the rst verb is moved to the front of

the sentence. is is wrong as well, however, for two reasons. One of the rea-

sons is sort of irrelevant for the present discussion; it has to do with sentences

like:

() a. Mar y le.

b. * Le Mary?

What this example shows is that the rule will have to be constrained so that it

moves only a certain class of verbs, and not so-called “main” verbs, verbs like

le . e class of verbs that the rule moves is called “auxiliary” verbs (or, AUX).ese verbs are: be, have, do and the modals: can, must , will , should , shall ,

could , would , etc. So the rule will have to be constrained so that it only moves

Auxiliary verbs. English doesn’t have a way of forming Yes/No questions from

sentences that don’t have Auxiliary verbs.



4 Kyle Johnson

e formulation of the rule cannot, as we suggested earlier, be simply:

“Move the rst auxiliary verb to the front of the sentence” because of examples

like the following.

() a. e woman that has kissed Bill might leave.

b. * Has the woman that kissed Bill might leave?

What we want is for the rule to produce ( ) from (a) instead.

() Might the woman that has kissed Bill leave?

What this example illustrates is that the notion “rst auxiliary” is not what

the rule makes reference to. e only way to get the rule to manipulate the

right verb is to make reference to the collection of words that make up the

subject. So our grammar must be able to make reference to groups of words.

ese groups are called “phrases”; and the subject of some sentence is the rst

Noun Phrase, a phrase that has a word of the category noun, in that sentence.

We can now express the rule as follows.

() S AUX I

Move the auxiliary verb that immediately follows the rst NP to the

front of the sentence.

Now that we’ve established that phrases exist, we can rephrase our rst task

in the following way: what are the correct arrangements of words that make

up some phrase. We can say that a Noun Phrase (NP) is made up of an initial

determiner, then an adjective, then a noun, as in:

() the brown fox

We write a Phrase-Structure rule to describe this possibility, as follows:

() NP → Det Adj N

Note that though the noun is an obligatory part of a noun phrase, neither

a determiner nor an adjective are. us, the following are possible noun

phrases.

() a. brown foxes

b. foxes

To represent the optionality of the determiner and adjective, we’ll place these

terms in parentheses; as in:

() NP → (Det) (Adj) NWhen more examples are considered, the rule that describes all possible

arrangements of categories that make up a noun phrase looks something like:

() NP → (Det) (Adj) N (PP) (CP)



Phrase Structure 5

“Det” stands for “determiner,” a category that includes the, a, some, many,

every, most and a few others. “Adj” stands for “adjective,” a category that

includes blue, bad , happy, friendly and scores of others. We will come back to

what these additional symbols represent. And I should also warn you that the actualrules allow for t remendously more complexNPs than this simple start would lead one to

expect.

A sentence is made up of some NP followed by a collection of words that

begins with a verb. is collection of words forms a phrase called a VerbPhrase, or VP, and is given by the following rules.

() VP → V (NP) (PP) (CP)

VP → AUX VP

Some examples are:

() a. eats

b. eats the beans

c. has eaten beans

And sentences themselves can have one of the two structures given below.

() S

→NP VP

S → CP VP

All the sentences we have seen up to now have the shape that the rst of these

rules describes: they are all sentences that start with a noun phrase and end

with a verb phrase. But it is possible to have sentences that start with other

sentences, this is what the “CP” is, as we shall see in a moment. An example of

this kind is ().

() [CP at Mary hogs chocolate] bothers me.

e “that Mary hogs chocolate” part of this sentence is a CP.

Sometimes two rules of the sort in (), which are identical up to one term,

are abbreviated as follows:

() S → NP

CP VP

e “curly brackets” (i.e., “{” and “}”) should be understood as enclosing a list

of options, exactly one of which must be chosen. us, () says that an S is

made up of either an NP or a CP at the beginning, followed by a VP.

e “PP” in these rules represents a group of words that contains a preposi-

tion, and forms a prepositional phrase. e following describes the shape that

these phrases take.

() PP → P NP

S

Some examples are:

() a. on the table b. for the woman

c. before the dance d. before John ran

e. because Sally eats beans f. behind the table



6 Kyle Johnson

We need one last phrase structure rule to be able to interpret all the

phrases named by our present rules. is is the rule that yields “CP,” or “Com-

plementizer Phrase,” as we shall call it. A CP is sort of like an S, except that it

always has a “subordinating particle” or “complementizer” word at the begin-

ning. So, for instance, in the following example, the group of words: that Peter

le is just a sentence with the word that , a complementizer, at the beginning.() Mary said that Peter le.

We have the following phrase structure rule, then:

() CP → C S

in which “C” stands for “Complementizer.” (Other complementizers are

whether and if .)

e phrases that words are arranged into, and that form sentences, can

be represented graphically with what are called “Phrase-Marker Trees.” An

example of a Phrase Marker Tree is ().

() S

NP

D

the

A

happy

N

child

VP

Aux

has

VP

V

eaten

NP

D

an

N

apple

We are now able to solve the problem posed by the existence of innitely

long sentences. Because the rules we have written so far are “recursive,” they

are able to generate innitely long, and innitely many, strings. e example

of innite length that we stumbled upon in () would be given the phrase

marker tree representation in () with these rules.



Phrase Structure 7

() S

NP

N

Sandy

VP

V

thought

CP

C

that

S

NP

N

Sally

VP

V

believes

CP

C

that

S

NP

N

John

VP

said .. .

ere is another context in which the innity of English sentences can be

seen, but this context calls for a change to the Phrase Structure rules we have

so far developed. It is possible for English verb phrases to have an indenite

number of prepositional phrases in them, as in:

() Mary walked [PP down the street] [PP over the hill] [PP through the woods] ....

Presently, however, our rule for VPs allows only one PP. One way of using

recursivity to capture these cases is to have two rules for VPs — one that

introduces PPs (recursively), and the others to build VPs of the sorts that we

have already seen. We might adopt something like (), for instance.

() VP → VP PP

VP → V (NP) (CP)

VP → AUX VP

is will give () the phrase marker tree, or parse, in ().



8 Kyle Johnson

() S

NP

N

Mary

VP

PP

P

down

NP

D

the

NP

N

street

VP

PP

P

over

NP

D

the

NP

N

hill

VP

PP

P

through

NP

D

the

NP

N

woods

VP

V

walked

Although the rules in () correctly allow for an indenite number of

Prepositional Phrases within a VPs, they aren’t quite right yet. ey have the

eect of putting PPs just at the right edge of a VP, and forcing all the other

phrases that a VP contains to come to their le. us, for instance, they allow

a Noun Phrase and a Prepositional Phrase to t inside a VP as in (), and not

as in ().

() S

NP

N

Sam

VP

PP

P

at

NP

N

noon

VP

V

met

NP

N

Sally



Phrase Structure 9

() *S

NP

N

Sam

VP

NP

N

Sally

VP

V

met

PP

P

at

NP

N

noon

is is the correct outcome, as it turns out, since ( ) is ungrammatical. But At least it’s usually judged ungrammaticalby English speakers if the sentence is utteredwith normal intonation.

the rules in () say the same thing about PPs and CPs, and this is incorrect.

Sentences such as () are perfectly grammatical.

() I suggested [PP to Sam] [CP that he buy chocolate].

We need to change () therefore so that it allows CPs to follow PPs.

It also turns out that there can be an indenite number of CPs inside VPs,

just as there can be an indenite number of PPs. us, for instance, we nd

sentences such as:

() Mary will dance [CP when Radiohead comes on] [CP if you ask her nicely] [CP which might be disturbing]. . .

To describe both these facts, we can change the rules we have in () so that

they also introduce CPs recursively, as in ().

() VP

→VP PP

VP → VP CPVP → V (NP)

VP → AUX VP

is will now give () the phrase marker representation in ().



10 Kyle Johnson

() S

NP

N

I

VP

CP

C

that

S

NP

N

he

VP

V

buy

NP

N

chocolate

VP

PP

P

to

NP

N

Sam

VP

V

suggested

So now we correctly allow either PPs or CPs to be the last phrase in a VP, but

force NPs to precede a PP and/or a CP that they share a VP with. With thesechanges to the rules that characterize VPs, we are now able to describe the

various ways in which VPs can be indenitely long. Although there are still

kinds of VPs that these rules do not describe, they describe enough of them

for the purposes of this class. ese will therefore be the rules for VPs that we

will use.

But some of our other rules will need to be further amended. We will want

to make changes to the rule that characterizes NPs, because they also seem

capable of having an indenite number of PPs and CPs within them, as, for

example, in:

() a. a ball [PP on the table] [PP behind the picture] [PP near the stapler] ...

b. a ball [CP that you bought] [CP that Sally now has] [CP that might go to Bill] . . .

Here too we might consider using additional NP rules, one that recursively

introduces PPs, one that recursively introduces CP, and another parallel to the

one we fashioned earlier.

() NP → NP PP

NP → NP CP

NP → (Det) (Adj) N

e NP in (a), for example, would consequently have the structure in ().



Phrase Structure 11

() NP

NP

PP

P

behind

NP

D

the

NP

N

picture

NP

NP

D

a

N

ball

PP

P

on

NP

D

the

N

table

PP

P

near

NP

D

the

NP

N

stapler

But there is additional complexity to NPs that we do not see in VPs. is

extra complexity arises because of the fact that adjectives too are capable of

coming an indenite number of times within NPs:

() the big, unhappy, hairy, unattractive, . . . dog

We will want to characterize this fact, like we have with PPs and CPs, by way

of a recursive rule. But, unlike the PP and CP situations, we can’t rely on a rule

like () because that will wrongly produce NPs like ().

() NP → Adj NP

() NP

A

unhappy

NP

D

the

N

dog

What we need, here, is a phrase inside NPs that recursively introduces ad-

jectives. is phrase is called an “N bar,” represented as N. We can use it to

introduce PPs and CPs too — and, in fact, we will later encounter facts which

suggest that this is correct. So, our rules building NPs will now look like this:

() NP → (D) N

N → A N

N → N PP

N → N CPN → N

is will give to a noun phrase like () a phrase marker representation like

that in ().



12 Kyle Johnson

() NP

D

the

N

A

big

N

A

unhappy

N

A

hairy

N

N

dog

And it will no longer give the NP in (a) the representation in (). Instead it

will give it the structure in ().

() NP

D

a

N

PP

P

near

NP

D

the

N

N

stapler

N

PP

P

behind

NP

D

the

N

N

picture

N

N

N

ball

PP

P

on

NP

D

the

N

N

table

ere is another change we will need to make to our rules for NPs. is

change is made necessary by the existence of the boldfaced noun phrases

in ().

() a. Mary’s book has appeared.

b. e woman’s book has appeared.

c. e man from Spain’s book has appeared.In these cases, there is another noun phrase found before a noun. is noun

phrase has an “s” appended to the end of it, and is said to be in the “posses-

sion” relation to the noun. So, for example, in (a), Mary is understood to

“possess” the book; and similarly for the woman and the man from Spain in the

(b) and (c). ese noun phrases have the structures indicated in ().



Phrase Structure 13

() a. NP

NP’s

N

N

Mary

N

N

book

b. NP

NP’s

D

the

N

N

woman

N

N

N

book

c. NP

NP’s

D

the

N

N

N

man

PP

P

from

NP

N

N

Spain

N

N

book

Notice, incidentally, that the determiner, the, in the b and c examples, is part

of the possessive noun phrase, and not part of the NP that contains it. at is,(b) isn’t parsed as:

() NP

NP’s

N

N

woman

D

the

N

N

book

In fact, it appears that a noun phrase in English can start with a determiner, or

it can start with a possessive NP, but it can’t start with both. We can discover

this by rst observing that certain kinds of noun phrases are prevented from

starting with a determiner. NPs that have just a name in them, for instance,

do not easily start with a determiner. is is indicated by the dierence in the

examples of ().

() a. the woman

b. * the Mary

Presumably this has something to do with the incompatible meanings of

names and determiners. Whatever the cause, we can now see from the con-trast in () that the determiner the must be within the possessive NP and not

the larger one.

() a. the book

b. * the Mary’s book



14 Kyle Johnson

e goodness of (a) shows that the can combine with book. erefore,

the badness of (b) must be because the in this example is prevented from

combining with book, and forced instead to be part of the possessive NP

containing Mary, which (b) has shown us isn’t good.

ese observations require that we change our NP rules so that they allow

Noun Phrases to start with a possessive NP, but only when that NP doesn’tstart with a determiner. is can be done by changing () to ().

() NP → (D) N

NP → (NP’s) N

N → A N

N → N PP

N → N CP

N → N

ese rules now allow an NP to start with either a determiner or a possessive

NP (both optionally).

ere is one last kind of sentence structure that we will consider and in-corporate into our set of Phrase Structure rules: coordination. Coordination

arises in cases, like (), where the word or , and , or but brings together two

strings of words (here in italics).

() a. e man visited the woman or the child .

b. e woman ran over the hill and through the woods.

c. e child crawled home and ate chocolate.

One fact about this construction is that the “coordinator,” as we shall call

the words or , and , and but , only brings together strings of words that t our

Phrase Structure rules. In the examples in (), the strings of words make up

an NP, in (a), a PP in (b) and a VP in (c). If we try to join strings thatdon’t t the rules which build phrases of these sorts, the result is ungrammati-

cal, as in ().

() a. * e man visited the or woman the child.

b. * e woman ran over and the hill through the woods.

c. * e child crawled home and child ate chocolate.

Further, the strings of words that are found on either side of the coordinator

must be the same kind of phrase. If the phrase to the right of and , for exam-

ple, is a PP, then so must the phrase that shows up to the le of and . If the

phrases on either side of the coordinator are not of the same kind, the result is

ungrammatical, as in ().

() a. * e man gave the book and to the woman.

b. * e happy and child le town.

We can describe these facts with the following pseudo-phrase structure rule.



Phrase Structure 15

() α → α coordinator α.

Where α ranges over any category label (like Noun, Verb, etc.) or phrase (like

NP, VP, etc.). is rule will now give (a) the phrase marker representation in

(a), and (c) the representation in (b).

() a. S

NP

D

the

N

N

man

VP

V

visited

NP

NP

D

the

N

N

woman

or NP

D

the

N

N

child

b. S

NP

D

the

N

N

child

VP

and VP

V

ate

NP

N

N

chocolate

VP

V

crawled

NP

N

N

home

is method of describing which arrangements of words (or more prop-

erly, categories) make grammatical English sentences has an interesting con-

sequence. ey specify how words are arranged linearly in terms of the way in

which they are grouped into phrases. So, for instance, they say that sentences

will be constructed in such a way that the string of words that starts the sen-

tence can be grouped into a noun phrase and all of those words will precede

the words that make up a verb phrase that ends the sentence. To be part of

the noun phrase that starts a sentence a word must precede every word that ispart of the verb phrase that ends that sentence. In a sense, the phrase structure

rules can be thought of as a function from the grouping of words into phrases

into their linear order. In certain cases, the phrase structure rules can group

words in dierent ways, but yield the same linear ordering of those words. We

say in these cases that the string of words is “structurally ambiguous.”



16 Kyle Johnson

To get a handle on cases of this sort, let’s begin by observing that the fol-

lowing string of words has more than one meaning. We say that it is “semanti-

cally ambiguous.”

() e boy hit the elf on the table.

is sentence can report that the elf on the table was hit by the boy, or itcan report that the hitting of the elf by the boy took place on the table. Now,

interestingly, this is one of those strings of words that can be given more than

one groupings into phrases by our phrase structure rules — it is structurally

ambiguous. Either the PP on the table can be parsed as part of the NP or not

as part of the NP. It has the two representations given below.

() a. S

NP

D

the

N

N

boy

VP

V

hit

NP

D

the

N

N

N

elf

PP

P

on

NP

D

the

N

N

table

b. S

NP

D

the

N

N

boy

VP

PP

P

on

NP

D

the

N

N

table

VP

V

hit

NP

D

the

N

N

elf

Is there a connection between this structural ambiguity and the meanings

that this sentence carries? I wish to convince you that there is a connection

and that the relationship between the various syntactic representations that

this sentence has and its meanings is given by the following rule.



Phrase Structure 17

() M R

A PP modies the phrase that it is a sister to.

α and β are if they are both dominated by exactly the same

nodes in a phrase marker tree.

is rule is a step towards completing the second goal of syntax that I outlined

earlier: it describes one of the relations between the arrangements of wordsand the meanings they convey. It assigns to (a) the rst interpretation de-

scribed above, the one in which it is the elf on the table which gets hit. And it

assigns to (b) the other interpretation, the one in which the hitting of the elf

happens on the table.

One reason for believing that there is a relationship between the structural

ambiguity of the string above and its semantic ambiguity is because this

hypothesis correctly predicts the number of meanings associated with strings

of this sort. To see this, consider the following example.

() I smashed the elf on the table with a hat.

is sentence has ve dierent meanings, depending on which phrase the PPs

on the table and with a hat modify. We might expect more than this number

of meanings as there are two PPs and three things that can be modied here:

VP, the rst NP and the second NP. But only ve emerge. is is predicted by

() since it makes the meanings that are available in cases like these depen-

dent on the syntactic representations that our phrase structure rules allow. In

(), our rules permit only ve dierent parses. ey are:

() S

NP

N

N

I

VP

PP

P

with

NP

D

a

N

N

hat

VP

PP

P

on

NP

D

the

N

N

table

VP

V

smashed

NP

D

the

N

N

elf

on the table and with a hat both modify smashed the elf :

“It’s on the table and with a hat that I smashed the elf.”



18 Kyle Johnson

() S

NP

N

N

I

VP

PP

P

with

NP

D

a

N

N

hat

VP

V

smashed

NP

D

an

N

N

N

elf

PP

P

on

NP

D

the

N

N

table

on the table modies elf and with a hat modies smashed the elf :

“It’s with a hat that I smashed the elf that was on the table.”

() S

NP

N

N

I

VP

V

smashed

NP

D

an

N

PP

P

with

NP

D

a

N

N

hat

N

N

N

elf

PP

P

on

NP

D

the

N

N

table

on the table and with a hat both modify elf :

“I smashed the elf that was on the table and had a hat.”



Phrase Structure 19

() S

NP

N

N

I

VP

V

smashed

NP

D

an

N

N

N

elf

PP

P

on

NP

D

the

N

N

table

PP

P

with

NP

D

a

N

N

hat

on the table modies elf and with a hat modies table:

“I smashed the elf that’s on the table which has a hat (on it).”



20 Kyle Johnson

() S

NP

N

N

I

VP

PP

P

on

NP

D

the

N

N

N

table

PP

P

with

NP

D

a

NP

N

N

hat

VP

V

smashed

NP

D

an

N

N

elf

on the table modies smashed the elf and with a hat modies table:

“It’s on the table with a hat, I smashed the elf.”

Documents

201syntax_psrules