A phrase is not a sentence or a clause, because it does not have a subject and a verb, and does not express a complete idea. It can act as a noun, an adjective, a preposition or an adverb. The function of a phrase depends upon its construction and place in a sentence.
Depending upon its function in a sentence, there are 9 different types of phrases - Noun Phrase, Verb Phrase, Adjective Phrase, Adverb Phrase, Gerund Phrase, Infinitive Phrase and Absolute Phrase.
A phrase which acts like a noun in a sentence is called a NOUN PHRASE, and contains a noun and other words like determiners and modifiers:
a brown dog.(noun phrase)
A noun phrase can be used wherever nouns are used in a sentence, such as the subject, or the object of a verb:
A brown dog bit me. (a brown dog = noun phrase subject)
I saw a brown dog. (a brown dog = object of a verb)
If a phrase acts like a preposition, and contains a preposition, then it is called a prepositional phrase:
The dog sat on the mat.(prepositional phrase)
Prepositional phrases have a noun or pronoun which is called the object of preposition.
A phrase that acts likes an adjective in a sentence is called ADJECTIVE PHRASE. Like an adjective it describes a noun or a pronoun.
She bought a beautiful green jacket. (adjective phrase)
A phrase that acts like an adverb in a sentence is called an ADVERB PHRASE. Like an adverb, it gives information about a verb, another adverb or an adjective, and it contains an adverb:
He spoke to me in a respectful way. (adverb phrase)
A verb phrase is the group of main verbs and helping-verbs (auxiliaries) within a sentence:
They are writing postcards. (verb phrase)
An infinitive phrase contains an infinitive and always acts like a noun, an adjective or adverb in the sentence:
I want to eat an apple. (infinitive phrase - noun)
I made a plan to help people. (infinitive phrase - adjective)
I played to win the match. (infinitive phrase - adverb)
A GERUND PHRASE uses the verb in the ING form but always acts like a noun in a sentence, so it can be used anywhere a noun can be used:
I hate eating fish. (gerund phrase)
A PARTICIPLE PHRASE is a phrase which contains either a present participle, and always acts like an adjective. It is always separated by commas.
The girl, playing with her hair, smiled sweetly. (participle phrase)
An ABSOLUTE PHRASE, which is also called a NOMINATIVE PHRASE consists of a noun or a pronoun and a participle. It looks like a clause but doesn't have a finite verb. It is always separated by commas.
Joe, having some free time, went to the library. (absolute phrase)