A phrase is a group of words related in such a way to express a basic concept but lacking either a verb or a subject, or both. (cf a clause which contains a subject)

A phrase can function as a verb, a noun, an adverb, or an adjective.

English phrases are usually larger than individual words, and are viewed as expansions of an individual word. At the same time they are smaller than clauses as they do not have subjects and verbs.

Phrases are classified into different types according to the type of head they have. The head is the central element of a phrase, and often it turns out to be the first word of the phrase.

Phrases which have a preposition as head are known as Prepositional Phrases.

Phrases which have a noun as head are known as Noun Phrases.

Phrases which have a verb as head are known as Verb Phrases.

Phrases which have an adjective as head are known as Adjectival Phrases.

Phrases which have an adverb as head are known as Adverbial Phrases.

Note: some phrases can be headless, like . This is a noun phrase consisting of a determiner (the) and an adjective (poor), but no noun.