Grammatical Functions of English Adjective Clauses

Adjective clauses are dependent clauses that consists of a relative pronoun followed by a clause and that perform adjectival functions. Adjective clauses perform four grammatical functions within sentences in the English language. The four functions of adjective clauses are:

Noun phrase modifier
Verb phrase modifier
Prepositional phrase modifier
Noun clause modifier

Some grammars use the term relative clause for adjective clauses. The following sections explain and exemplify the four grammatical functions of adjective clauses in English grammar.

Adjective Clauses as Noun Phrase Modifiers

The first grammatical function that adjective clauses 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 adjective clauses function as noun phrase modifiers:

Harry Potter is the boy who lived.
The map you sent me last week seems outdated.
The cookies, which I promptly devoured, reminded me of home.
My aunt is the woman to whom you should have emailed the instructions.
A book that you ordered through interlibrary loan arrived this morning.
The neighbor whose petunias you ran over with the lawn mower called the cops on you.

Adjective clauses most frequently function as noun phrase modifiers.

Adjective Clauses as Verb Phrase Modifiers

The second grammatical function that adjective clauses perform is the verb phrase modifier. A verb phrase modifier is a word, phrase, or clause that modifies or describes a verb phrase. Adjective clauses modify only verb phrases in the form of present participles performing nominal functions. Only which adjective clauses function as verb phrase modifiers. For example, the following italicized adjective clauses function as verb phrase modifiers:

Reading, which is one of my favorite past times, keeps the mind sharp.
Washing the windows, which still needs completed, occurs every Wednesday morning.
I enjoy writing about language, which I do almost every single day.
Hunting tigers, which many people still consider sport, should be outlawed internationally.
The hardest part about learning grammar, which I thoroughly enjoy, is memorizing all the rules.
Despite our missing the train, which happened because of a traffic jam, we arrived on time.

Adjective Clauses as Prepositional Phrase Modifiers

The third grammatical function that adjective clauses perform is the prepositional phrase modifier. A prepositional phrase modifier is a word, phrase, or clause that modifies or describes a prepositional phrase. Adjective clauses modify only prepositional phrases performing nominal functions. Only which adjective clauses function as prepositional phrase modifiers. For example, the following italicized adjective clauses function as prepositional phrase modifiers:

Behind the machine shed, which is overgrown with weeds, needs mowed.
Between seven and nine, which is a reasonable time frame, is when employees must arrive.
In the closest, which is quite dark, is rather scary.
After six, which is usually also after dinner, is a good time to call.
You must clean under the bed, which is covered with dust bunnies.
His brother is painting along the ceiling, which is ragged and uneven.

Adjective clauses rarely function as prepositional phrase modifiers because prepositional phrases rarely perform nominal functions.

Adjective Clauses as Noun Clause Modifiers

The fourth grammatical function that adjective clauses perform is the noun clause modifier. A noun clause modifier is a word, phrase, or clause that modifies or describes a noun clause. Only which adjective clauses function as noun clause modifiers. For example, the following italicized adjective clauses function as noun clause modifiers:

That the museum cancelled the lecture, which is quite surprising, disappoints me.
For you to not graduate from college now, which would be such as shame, is out of the question.
That she worked hard for the whole term, which still amazes me, pleased her parents.
How the clouds drifted on that July afternoon, which still makes me smile, may never happen again.
Do you know when the train should arrive, which is something I should know?
The assessment committee announced the problem us refusing to try new procedures, which is an ongoing challenge.

The four grammatical functions of adjective clauses in English grammar are noun phrase modifier, verb phrase modifier, prepositional phrase modifier, and noun clause modifier.

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.