IV. Syntactic structure ( 1 )

– phrases, constituents, phrase markers, PS rules

Syntactic structure

Sentences are not just sets of words. Words in a sentence are interrelated in several different ways. The network of these relationships is what we call syntactic structure.

The two basic relations among words in a sentence are:

a) linear ordering (e.g. A precedes B)

b) composition (e.g. A and B combine to form a higher level unit - a phrase)

The syntactic units (called constituents) are thus:

a) words

b) phrases

The syntactic structure is often called a constituent structure or phrase structure

Phrase – a syntactic unit consisting of;

a) a head word

b) other syntactic units (words or phrases) related to the head – the modifiers.

Modifiers usually are in certain semantic relation to the head – provide some additional specification in term of properties and qualities of whatever the head word denotes, e.g.:

[ very pretty ] head+1 modifier

[ thesevery pretty girls ] head + 2 modifiers

[ knew these very pretty girlswell ] head + 2 modifiers

(underlined – modifiers, boldfaced – head words)

2. Classification of phrases

Like words, phrases are grouped into classes (syntactic categories). The basic criterion for classification is the similarity of their syntactic properties (like their potential positions in a sentence, i.e. their distribution).

The distribution of a phrase is determined by the class of its head word.

Therefore, the phrases with the head words of the same type are grouped together and the name of the phrase type is derived from the name of the class of its head word (the phrase with N as its head is an NP, the VP has a V as its head etc)

NP

John talks about animals

new movies

the last king of France

that idea that I told him about

* kill animals

* very quickly

VP

He may come

go home now

say that John kissed Mary

*these tall pictures

* eager to do it,

3. Two equivalent ways of representing CS

a) bracketing b) tree diagrams (nodes connected by branches)

X root node

[ [ a + b ] + c ] node Y branch

X Y

terminal node

a b c

X and Y = syntactic category labels

A representation of the phrase structure of a sentence in form of a tree diagram or bracketed string which shows division into constituents and labels constituents with the symbols of their syntactic categories is called a Phrase Marker.

Example:

tree diagram:

S

NP VP

Det Adj N V PP

P NP

Det N

this tall boy talked to that girl

labeled bracketing:

[ [ [this] [tall] [boy]] [ [talked] [ [to] [ [that] [girl] ] ] ] ]

S NP Det A N VP V PP P NP Det N

The phrase markers above show a greatly simplified phrase structure of an English sentence.

We will propose later several modifications and corrections to these representations.