In everyday speech, a phrase may refer to any group of words. In linguistics, a phrase is a group of words (or sometimes a single word) that form a constituent and so function as a single unit in the syntax of a sentence. A phrase is lower on the grammatical hierarchy than a clause.[1]
Examine the following sentence:
- The house at the end of the street is red.
The words in bold form a phrase; together they act like a noun. This phrase can be further broken down; a prepositional phrase functioning as an adjective can be identified:
- at the end of the street
Further, a smaller prepositional phrase can be identified inside this greater prepositional phrase:
- of the street
And within the greater prepositional phrase, one can identify a noun phrase:
- the end of the street
Phrases can be identified by constituency tests such as proform substitution (=replacement). For instance, the prepositional phrase at the end of the street could be replaced by an adjective such as nearby: the nearby house or even the house nearby. The end of the street could also be replaced by another noun phrase, such as the crossroads to produce the house at the crossroads
Most phrases have an important word defining the type and linguistic features of the phrase. This word is the head of the phrase and gives its name to the phrase category.[2] The heads in the following phrases are in bold:
- too slowly - Adverb phrase (AdvP)
- very happy - Adjective phrase (AP)
- the massive dinosaur - Noun phrase (NP)
- at lunch - Preposition phrase (PP)
- watch TV - Verb phrase (VP)
The head can be distinguished from its dependents (the rest of the phrase other than the head) because the head of the phrase determines many of the grammatical features of the phrase as a whole. The examples just given show the five most commonly acknowledged types of phrases. Further phrase types can be assumed, although doing so is not common. For instance one might acknowledge subordinator phrases:
- before that happened - Subordinator phrase (SP)
This "phrase" is more commonly classified as a full subordinate clause and therefore many grammars would not label it as a phrase. If one follows the reasoning of heads and dependents, however, then subordinate clauses should indeed qualify as phrases. Most theories of syntax see most if not all phrases as having a head. Sometimes, however, non-headed phrases are acknowledged. If a phrase lacks a head, it is known as exocentric, whereas phrases with heads are endocentric.
