Syntax - 3 Constituents, Phrasal (Syntactic) Categories and Phrase Structure (Syntactic) Rules

Syntax –  Constituents, Categories and Phrase Structure Rules

A. Constituents

Constituents are the units which may be words, phrases (groups of words not qualifying as sentences) or clauses (sentences embedded in lager sentences) that go into the making of a larger structure.

 For example, the sentence – Boys are naughty – has three constituents all of which are words. In the sentence – The naughty boy broke the glass, - again, we have three constituents two of which are noun phrases and the third one is a verb. In the sentence – The boy who is naughty broke the glass – we have a clause (a sentence within a sentence)  - 'who is naughty' - as a constituent of a larger sentence.

Traditional grammar operated with words as the constituents of sentences. The words were then classified into parts of speech such as nouns, pronouns, verbs, adjectives, adverbs etc. But modern grammarians have rejected this classification because

1. Their definitions are vague and imprecise.

2. Words belonging to the same part of speech are not always inter-substitutable in larger structures.

3. The same word form sometimes functions as different parts of speech in different structures.

4. The parts of speech are not universal. Some languages do not draw a distinction between nouns and verbs, others do not distinguish between verbs and adjectives and so on.

Modern grammarians therefore operate with phrasal categories. All the phrases in a phrasal category are inter-substitutable in all the well-formed sentences of a language. In other words, they have the same distribution in all the sentences of the language in question.

The idea of constituent structure was first given by Bloomfield. It was further developed by his followers out of whom Chomsky is the most notable.

According to phrase structure grammars, words, the ultimate constituents of sentences, do not combine with one another directly to generate the final structure. They combine with one another in a hierarchical manner. The ultimate constituents combine with some others to generate the intermediate constituents. The intermediate constituents of the second level then combine to generate the constituents of the next higher level. And this process goes on until we reach the final structure.

So while analyzing the structure of a sentence, we do not straightaway analyse into its ultimate (final) constituents. We first analyse into its immediate constituents which are the intermediate constituents. These intermediate constituents are then analysed into smaller constituents of the next lower level. The process goes on until we reach the constituents which can no longer be analysed into smaller constituents. These smallest constituents which cannot be analysed further into smaller ones are the ultimate constituents of the given sentence. 

Tree Diagram Showing the Constituent     Structure of a Sentence

We shall take up the following sentence and analyse it to see its constituent structure:

Sentence - The people in the room will move the desk into the hall

                                                                       S

                                               ←←←←←←←→→→→→→→

                                             ↓                                                      ↓                                         

                                           NP                                                    VP

                               ←←←→→→→                                ←←←→→→→

                              ↓                          ↓                              ↓                          ↓

                            NP                        PP                           VP                       NP

                  ←←←→→             ←←→→               ←←→→          ←←←→→→

                 ↓                 ↓            ↓               ↓            ↓            ↓          ↓                      ↓              

               Art               N            P              NP        Aux        V         NP                    PP  

                 ↓                ↓             ↓        ←←→→     ↓           ↓     ←←→→         ←←→→

                 ↓                ↓             ↓       ↓             ↓     ↓           ↓    ↓              ↓       ↓              ↓                    

                 ↓                ↓             ↓     Art           N     ↓           ↓   Art           N      P             NP

                 ↓                ↓             ↓       ↓             ↓     ↓           ↓    ↓              ↓      ↓        ←←→→

                 ↓                ↓             ↓       ↓             ↓     ↓           ↓    ↓              ↓      ↓       ↓              ↓ 

                 ↓                ↓             ↓       ↓             ↓     ↓           ↓    ↓              ↓      ↓     Art             N

                 ↓                ↓             ↓       ↓             ↓     ↓           ↓    ↓              ↓      ↓       ↓              ↓

             The           people        in     the        room will   move  the         desk into    the           hall

The sentence is first analysed into two constituents – NP (The people in the room), and VP (will move the desk into the hall). The NP is then analysed into two constituents – NP (The people) and PP (in the room). The NP is then analysed into two constituents – the determiner which is an article (the) and the noun (people). The PP (in the room) is then divided into two constituents - the preposition P (in) and the NP (the room). The NP is analysed into two constituents - the determiner which is an article (the) and the noun (room).
The VP is analysed into two constituents – the VP (will move), and the NP (the desk into the hall). Next, the VP is analysed into two constituents - the auxiliary (will) and the verb V (move). The NP (desk into the hall) is then divided into two constituents - the NP (the desk) and the PP (into the hall). Then the NP is divided into two constituents, the determiner which is an article (the) and the noun (desk). The PP is further divided into two constituents – the preposition P (into) and the NP (the hall). The NP is then divided into two constituents – the determiner which is an article (the) and the noun (hall). We have now reached a level where no further division is possible. So the ultimate constituents of the sentence are – The – people - in - the - room - will – move – the – desk – into – the – hall.

Conversely, moving from the bottom to the top, we can say that the determiner ‘the’ and the noun ‘people’ combine to constitute the NP ‘the people’. Similarly, the determiner ‘the’ and the noun ‘room’ combine to constitute another NP ‘the room’. In the same way, we get the NPs ‘the desk’ and ‘the hall’. The preposition ‘in’ is then attached to the NP ‘the room’ to form the PP ‘in the room’ and the preposition ‘into’ is attached to the NP ‘the hall’ to form another PP ‘into the hall’. Next, the NP ‘the people and the PP ‘in the room’ are combined to form the NP ‘the people in the room’. The Auxiliary (will) and the verb ‘move' are then combined to form the VP (will move). Next, the NP ‘the desk’ and the PP 'into the hall' are combined to obtain the NP ‘ the desk into the hall’. Then the VP ‘will move' and the NP 'the desk into the hall’ are combined to obtain the larger VP ‘will move the desk into the hall’. Finally, the NP ‘the people in the room’, and the VP ‘will move the desk into the hall’ are combined to get the sentence ‘The people in the room will move the desk into the hall’.

It is clear that the constituents that come together to form a larger constituent of the higher level are more closely related to one another than to the other constituents to yield a sensible meaning. If any of them is attached to any other constituent, the result will be a non-sense phrase not acceptable in the language. For example, we cannot combine ‘the people’ with ‘in to get an intermediate constituent ‘the people in’. Nor can we combine ‘the room’ with ‘will’ to get another intermediate constituent ‘the room will’.    

Phrase Structure Rules 

or

Syntactic Rules

Phrase structure rules are a type of rewrite rules used to describe a given language's syntax. They are closely associated with the early stages of transformational grammar, proposed by Noam Chomsky in 1957. They are used to break down a natural language sentence into its constituent parts known as syntactic categories which include both lexical categories (parts of speech) and phrasal categories.

Phrase structure rules tell us what the constituents of a phrase are and how they are ordered. They help us to analyse the structure of a sentence in order ti understand its meaning. We can also use them to generate more sentences of the same type by selecting different constituents of the appropriate categories and joining them in accordance with the rules. 
Constituents are words or groups of words that make up a unit and can be combined to make up larger grammatical units.

The phrase structure rules are written as follows:

A ⇢  B C       or as          A ⇢ B + C

Which means

Rewrite A as B followed by C 
or 
A consists of B followed by C.

We can have rules like the following for different types of structures:

1. Sentence

S →   NP Aux. VP

A sentence consists of an NP followed by an auxiliary which is then followed by a VP.

2. Noun Phrase

NP⇢ (Det.) (Adj.) N (PP)

   A noun phrase may consist of a determiner, an adjective, a noun and a prepositional phrase. The noun is the head and it is an obligatory element. The other three elements given in brackets are optional.

3. Prepositional Phrase

PP⇢ P NP    
A prepositional phrase consists of a preposition followed by an NP                                           

4. Adjective Phrase

Adj. P⇢ (Adv.) Adj.                 Very noble

An adjective phrase consists of an adjective which may optionally be modified by an adverb.

5. Adverb Phrase

Adv. P⇢  (Adv.)    Adv.                                 Very honestly

An adverb phrase consists of an adverb which may optionally be modified by another adverb.
Using the PS rules, the structure of the sentence 'The boy is reading a book.'can be anallysed as follows:

S  NP VP
VP  VP NP
VP  Aux. V
NP  Det. N
V  ing + read
Aux.  tense be
N   (boy, book)
Det.  (the\0
using the same rules, we can then generate the sentence - The girl is making a doll.
It is not necessary to write the rules in a given order. We may use a different order without making any difference to the rules.

B. Phrasal Categories

In the Chomskyan theory of syntax, the traditional Parts of Speech labels have been replaced by phrasal categories. A phrasal category is a group of units which can be substituted for one another in a structure of a higher level. The units forming a phrasal category may consist of a single word or a number of words grouped together into a phrase or even a sentence (clause).

The names given to these phrasal categories have been borrowed from the traditional parts of speech labels. A phrase is named after the name of the part of speech label assigned to the word that heads the phrase. Thus, a noun phrase (NP) is a phrase headed by a noun, a verb phrase is a phrase headed by a verb, a prepositional phrase is a phrase headed by a preposition, an adjective phrase is a phrase headed by an adjective and an adverb phrase is a phrase headed by an adverb.

C. Classification and Internal Structure of Syntactic Categories (Phrasal Categories)

Noun Phrase

A noun phrase is a phrase having a noun as its head. It may consist of a noun or a pronoun only. Thus, John, honesty, and he are noun phrases consisting of a single word which is a noun or a pronoun.

 A noun heading a noun phrase may be preceded by a determiner (an article or a word like some, many, few, a few, any, all etc.). A man, an alligator, the book, some people, all boys, a few students etc. are noun phrases having man, alligator and book, people, boys and students as their head.

The noun may be pre-modified by an adjective, a noun, a present participle or a past participle as is clear from the following examples.

A noble man (adjective as modifier)

A mill worker (noun as modifier)

An interesting story (present participle as modifier)

A frustrated man (past participle as modifier)  

NP⇢ (Det.) (Adj.) N (PP)

                                                      NP                             

                                                   ↙       ↘

                                              Det.        NP

                                               ↓         ↙      ↘

                                              ↓       Mod       N

                                              ↓         ↓           ↓

                                              A      noble    man

   NP = Noun Phrase       Det. - Determiner      Mod. = Modifier         N = Noun

It may also be post-modified by a prepositional phrase, a present participle phrase, a past participle phrase or even by an adjective clause.

The boy on the last bench (post-modification by a prepositional phrase)

The boy sitting on the last bench ((post-modification by a present participle phrase)

The boy seated on the last bench (post-modification by a past participle phrase)

The boy who is sitting on the last bench (post-modification by an adjective clause)

While analysing the deep (underlying) structure of a sentence, post modification by a participle phrase or an adjective clause is treated as an embedded sentence.

Prepositional Phrase

A prepositional phrase is a phrase headed by a preposition which is placed initially in the phrase.    

On the last bench in the above examples is a prepositional phrase.

A prepositional phrase, as we can see, consists of a preposition followed by a noun phrase.

PP → Preposition + NP

                                                                 On the last bench

PP

↙        ↘

                                                      Preposition        NP

                                                           On               the last bench

                                                           ↓                      ↙       ↘

                                                           ↓                   Det.         NP

                                                           ↓                   ↓              ↙  ↘

                                                           ↓                   ↓        Mod.   N

                                                           ↓                   ↓           ↓       ↓

                                                          On                 the       last   bench

       PP = Prepositional Phrase    P= Preposition     NP = Noun Phrase   
       Det.= Determiner           Mod. - Modifier         N = Noun

Verb Phrase

A verb phrase is a phrase having a verb as its head. The verb in the phrase occupies the initial position in the phrase.

In the sentence ‘The parrot sat in the tree.’, ‘sat in the tree’ is a verb phrase.

Sometimes, the verb is preceded by an auxiliary. Some linguists treat the auxiliary as a separate element while others treat it as a part of the verb phrase.  If a sentence contains an auxiliary, and the auxiliary is treated as a separate element, we have to analyse the sentence into three units instead of two. But in the IC analysis, we treat the auxiliary as a part of the verb phrase. So it is combined with the verb phrase and the sentence is analysed into two immediate constituents - the NP and the VP.

                                                            

                                                      S

                                    ←←←→→→
                                   ↓                       ↓

                                 NP                     VP

                           The cat                is running after the rat.

                          ←←→→                 ←←←→→→  
                         ↓             ↓                ↓                      ↓                     

                        Det          N               VP                   PP

                         ↓             ↓                ↓                      ↓

                        The         cat         is running         after the rat.

                         ↓             ↓           ←←→→           ←←←←→→
                         ↓             ↓          ↓              ↓         ↓                     ↓

                         ↓             ↓        Aux           V        P                    NP

                         ↓             ↓          ↓              ↓         ↓                      ↓

                         ↓             ↓         is       running    after             the rat

                         ↓             ↓         ↓                ↓         ↓             ←←→→

                         ↓             ↓         ↓                ↓         ↓            ↓               ↓

                         ↓             ↓         ↓                ↓         ↓         Det              N

                         ↓             ↓         ↓                ↓         ↓           ↓                ↓  
                       The         cat        is         running   after      the              rat

                         

S = Sentence             VP = Verb Phrase          PP = Prepositional Phrase         P= Preposition          

 NP = Noun Phrase      Det. - Determiner         N = Noun    Aux. = Auxiliary

Adjective phrase     

An adjective phrase is a phrase headed by an adjective.

In the NP ‘a very noble man’, ‘very noble’ is an adjective phrase with the adjective noble as the head and the adverb very as its modifier.

As we have seen, an adjective can be modified by an adverb in an adjective phrase.

     

                                                 Very Noble

                                                  Adjective Phrase

                                                      ↙  ↘

                                               Mod.    Adj.        Mod. = Modifier         Adj. = Adjective

The adjective in an adjective phrase may also be modified by a clause of comparison as in

The boy has grown as tall as his father.

Adverb Phrase

An adverb phrase is a phrase having an adverb as its head. In the sentence

He performed his duty very honestly

‘very honestly’ is an adverb phrase. Honestly, which is an adverb, is its head. ‘Very’ is another adverb which modifies the adverb ‘honestly’. We see that the head in an adverb phrase may itself be modified by another adverb.

                                                                 Very honestly

                                                                Adverb Phrase

                                                                        ↙  ↘

                                                                very       honestly

It may also be post-modified by a clause of comparison as in the following sentence.

He ran as fast as he could.