Adjective phrases including adjectives perform four main grammatical functions within sentences in the English language. The four functions of adjectives and adjective phrases are:
Adjectives are traditionally defined as “words that describe nouns.” Adjective phrases are defined as phrases that consist of an adjective plus any modifiers or complements such as adverbs, prepositional phrases, verb phrases, and noun clauses.
Adjectives as Adjective Phrase Heads
The first grammatical function that adjectives perform is the adjective phrase head. An adjective phrase consists of an adjective plus any modifiers or complements. For example, the following italicized adjectives function as adjective phrase heads:
- extremely large
- fond of ice cream
- afraid to try new foods
- hopeful that the rain would stop
Noun Phrase Modifiers
The second grammatical function that adjectives and adjective phrases perform is the noun phrase modifier. A noun phrase modifier is a word, phrase, or clause that modifies or describes a noun including a pronoun or a noun phrase. For example, the following italicized adjectives and adjective phrases function as noun phrase modifiers:
- My mother planted purple flowers in her garden.
- The very tiny puppy barked at the cat.
- The restaurant served plain, tasteless soup.
- The committee picked somebody stupid for our new leader.
- Barack Obama was the president elect.
The third grammatical function that adjectives and adjective phrases perform is the subject complement. A subject complement is a word, phrase, or clause that follows a copular, or linking, verb and describes the subject of a clause. The term predicate adjective is also used for adjective phrases that function as subject complements. For example, the following italicized adjectives and adjective phrases function as subject complements:
- Under the bed is filthy.
- The cake tastes sickenly sweet.
- My cat is black and brown.
- Your perfume smells especially musky but very nice.
- I am fond of English grammar.
The fourth grammatical function that adjectives and adjective phrases perform is the object complement. An object complement is a word, phrase, or clause that directly follows and modifies the direct object. For example, the following italicized adjectives and adjective phrases function as object complements:
- The farmer painted the barn red.
- The little girl wanted her room bright pink.
- Catholics consider saints holy.
- The jury judged the defendant guilty.
- My puppy makes me happy.
Adjectives Versus Adverbs
Although not accepted in standard English, adjectives and adjective phrases also function as verb phrase modifiers and adverbials. For example, the adjective phrase too loud in the sentence He plays his music too loud functions as verb phrase modifier. However, standard prescriptive grammar rules dictate that only the adverb phrase too loudly should function as the verb phrase modifier in this instance. Another example is the adjective careful functioning as an adjunct adverbial in the sentence Drive careful. Again, prescriptive rules state that the adverb carefully should function as the adjunct adverbial. However, the use of adjectives and adjective phrases as verb phrase modifiers and adverbials is accepted in many forms of spoken English.
The four grammatical functions of adjectives and adjective phrases in English grammar are adjective phrase head, noun phrase modifier, subject complement, and object complement.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.