3.1        Constituents and constituent structure

v  The fundamental concept of this chapter is that sentences are not just strings of words, but have a more complex structure, which linguists call Constituent Structure.

Consider the following sentence:

(1)   John angered Mary.

       It consists of three words, two nouns and separated by a verb.

(2)   The big dog angered the cat.

       It contains six words. Three words, the big dog, seem to play the same role in (2) that one word, John plays in (1).

(3)   [The big dog] angered [the cat]

       It has three chunks , even though it has a different number of words. Chunks of linguistic material like those enclosed in bracket (3) are called CONSTITUENTS. The hierarchical structure of sentences and other utterances is called CONSTITUENT STRUCTURE.

v  The basic organization of (3) is not a string of six words, but a rather a string of three constituents.

3.2   Syntactic categories

v  We can also scramble things a bit and produce other sentences that are parallel to (2) and (3)

 (4) The cat angered John.

       Mary angered the big dog.

John, Mary, the big dog, and the cat are the same type of constituents, since they are Mutually Substitutable for each other. This type of constituent is traditionally called a NOUN PHRASE (NP). To show the noun phrse in a sentence, we can label the brackets.

(5)   [NP The big dog] angered [NP the cat]

     Here are some other noun phrases in English.

(6)   many people

       two big, bad bullies

       Arthur and his brother

       A shy entelope

v  Articles such as the, a, and an, as well as demonstrative such as this and that form another syntactic category, and can be formed in a noun phrase.

(7)   the old man

       an old man

       this old man

   With these additional syntactic categories, we can add more labeled brackets and identify all the constituents in (5).

(8)   [S  [NP [D The] [A big] [N dog] ]  [VP [V angered] [NP [D the] [N cat] ] ]   ]

Bracketed this way, it is clear that certain strings in this sentence are not constituents, big dog is not a constituent, because it is not complete. The big dog angered is not a constituent, because it has too many words to be a noun phrase and not enough to be a clause. For a string of words to be a constituent, there must be a matched pair of bracket s that encloses the entire string and nothing but the string.

     We can say, the, big, dog are each CONSTITUENTS OF the first NP and the and cat are each constituents of the second NP. Also, the verb and the second NP are constituents of the VP. The only two constituents of the clause are the first NP and the VP.

3.3 Comparing syntax and morphology

       Syntactic categories differ in size and expandability; some are OPEN CLASSES and some ore CLOSED CLASSES. Most  syntactic categories, like N and V, are open classes, since new nouns and verbs can be added freely to vocabulary.

       There is also correlation between the openness of a class and the meaning of its members. Open classes like nouns almost always have LEXICAL MEANING, while closed classes like determiners usually have GRAMMATICAL MEANING. The members are MUTUALLY SUBSTITUTABLE for each other.

3.4   Trees

•   As we have seen, sentences are not just strings of words. Words combine to make larger constituents called phrases, phrases combine to make larger constituents called clauses, and so forth. A convenient device for displaying the constituents structure is called a TREE or TREE DIAGRAM.

•        The lines in the trees are called BRANCHES, and the labeled places at the end of the lines are called NODES. The topmost node on a tree is often called the ROOT node; the root nodes in the tree in (9) are labeled S. The bottommost nodes are called LEAVES or TERMINAL NODES; they are labeled with specific words like the and angered.

3.      5   Auxiliary verbs

•        Many languages have a subclass of verbs called AUXILIARY VERBS or AUXILIARIES. Examples in English include words like should, have, and be, which are used in combination with other verbs and that contains another VP embedded inside it.
•        What is special about an auxiliary verb is that it requires a second VP to be present in the tree, just like a transitive verb requires a direct object to be present. In other words, auxiliaries subcategorize for VPs. In (10), the VP take the Cadillac occurs alongside the auxiliary should, thus satisfying its subcategorization requirement. It is this second VP that contains the ‘main’ verb.