Speakers of any language have the ability to intuitively judge whether or not a sentence is grammatical, or well-formed. For example, speakers of English know that (1) is acceptable and (2) is not, even without necessarily understanding why.
(1a) Wise teachers listen to their students.
(1b)* Listen to their students wise teachers.
This ability to make these judgments is based on the constraints specific to one’s language that govern how phrases may be constructed. We refer to these as phrase structure rules (PSR). In other words, phrases that adhere to PSRs will be judged as grammatical (1a), those that don’t will be judged as ungrammatical (1b).
If we look at the difference between (1a) and (1b), we see that the order of constituents in (1a) is subject – verb – object that is obligatory in English, whereas in (1b) the order is verb-object – subject. These sentences generate the PSRs that explain our grammaticality judgments.
(2a) S —> NP, VP 1
(2b) *S —>VP, NP
Let’s look at the structure of an NP. Consider (3a) and (3b).
(3a) [Wise teachers] listen to their students.
(3b) *[Teachers wise] listen to their students.
First, and most basically, we know that an NP must have a head ‘N’. Thus we can stipulate the following rule:
(4) NP —> N
We also know that Ns may optionally be modified by an adjective, ‘AP’ in which case ‘A’ must precede N. When this occurs the phrase is grammatical (3a); when A follows N the phrase is ungrammatical (3b), shown in (5a) and (5b). Now we understand why (3b) is not acceptable. English does not permit an adjective to follow the N it modifies. The PSRs below demonstrate this knowledge.
(5a) NP —> (AP) N
(5b)* NP —> N (AP)
Now we have two PSRs for NPs in English.
Consider (6a) and (6b).
(6a) [The students] respect attentive teachers.
(6b) * [Students the] respect attentive teachers.
Here we see that the placement of a determiner (D) in relation to the N it modifies also affects grammaticality. When D precedes N, the phrase is acceptable (7a); when it follows, the phrase is unacceptable (7b).
(7a) NP —> (D) N
(7b)* NP —> N (D)
Now we have three PSRs for NPs. (4), (5a), and (7a).
Consider VPs in English by examining the following sentences.
(8a) Lois [smiled].
(8b) *Lois [smiled flowers].
(8c) *Lois [bought].
(8d) Lois [bought flowers].
(8e) *Lois [flowers bought].
(8f) Lois gave flowers [to her mother].
(8g) Lois gave flowers [to her mother [on her birthday, [after dinner, [on the balcony]]]].
First, VPs must contain a V head, thus (9).
(9) VP —> V
However certain verbs require an NP direct object (8d) while others may not select one (8a). We also know that NPs must follow verbs of which they are direct objects (8e). The optionality and position of an NP in VP is shown in (10).
(10) VP —> V (NP)
We see that certain verbs require an indirect object that will be generated in a PP, (8f) and that any number of PPs may be added to the VP (8g).
(11) VP —> V (NP) (PP*)
There are also verbs that select a sentence as a complement, with the ability to add as many as desired. Thus a structure such as (12) will yield (13).
(12) Lois hopes [that her mother will like the flowers [that she bought]].
(13) VP —> V (NP) (PP*) (S*)
In order to simplify (13), we can state VP V (NP) ({PP, S}*), the curly brackets showing that both PP and S are optional and may be repeated.
These are just a few PSRs of English. Below is a more complete list.
- S —> NP VP
- NP —> (D) (A*) N ({PP,S}*)
- VP —> V (NP*) (AP) ({PP,S}*)
- PP —> P NP
- AP —> (Adv*) A ({PP,S}*)
Now we have a theory that explains our intuitions on which structures are grammatically acceptable and which are not.
Remember the symbols for abbreviations:
- (X) = optional X
- X* = any number of Xs
- {X, Y} = either X or Y
For practice at these PSRs, go to syntax exercises and click on Syntax: Phrase Structure Rules Level 1.
1Abbreviations for syntactic categories
- S- sentence
- NP- noun phrase
- N-noun
- D-determiner
- VP-verb phrase
- V-verb
- AP-adjectival phrase
- A-adjective
- AdvP-adverbial phrase
- Adv- adverb
- PP-prepositional phrase
- P-preposition
McHugh, Aronow