Relative Clause

A relative clause is one kind of dependent clause. It has a subject and verb, but can’t stand alone as a sentence. It is sometimes called an “adjective clause” because it functions like an adjective—it gives more information about a noun. A relative clause always begins with a “relative pronoun,” which substitutes for a noun, a noun phrase, or a pronoun when sentences are combined.

The relative pronouns are:

who	for people	can substitute for subject nouns/pronouns (he, she, we, they)
whom	for people	can substitute for object nouns/pronouns (him, her, us, them)
whose	for people	can substitute for possessive nouns/pronouns (his, hers, our, their)
that	for people or things	can be either subject or object can only be used in restrictive relative clauses (see below)
which	for things	can be either subject or object can be used in non-restrictive relative clauses can also be used in restrictive relative clauses, though some people don’t like this use

Relative pronoun as subject (in red):

I like the person. The person was nice to me.

I like the person who was nice to me.

I hate the dog. The dog bit me.

I hate the dog that bit me.

I am moving to Louisville, KY. It is home to the Muhammad Ali Museum.

I am moving to Louisville, KY, which is home to the Muhammad Ali Museum.

Relative pronoun as object (in red):

I like the bike. My father gave me the bike.

I like the bike that my father gave me.

Restrictive Relative Clauses

Restrictive relative clauses give information that defines the noun—information that’s necessary for complete identification of the noun. Use “that” or “which” for non-human nouns; use “that” or “who” for human nouns. Do not use commas.

I like the paintings. (Which paintings? We can’t clearly identify them without the relative clause.)

So we add the clause:

The paintings hang in the SASB North lobby.

I like the paintings that hang in the SASB North lobby.

OR

I like the paintings which hang in the SASB North lobby. (Again, this is acceptable, but some people object to using “which” in a restrictive relative clause. “That” is preferred.)

Students who study hard will do well in my class. (Only this group of students will do well.)

Students whose grades are low can drop one test score. (Only this group can drop a test score.)

When the noun is the object of the preposition, both the noun and the preposition move together to the front of the relative clause. In less formal English, it’s common to move only the pronoun to the front of the clause.

I spent hours talking with a person last night. I hope to hear from her.

I hope I hear from the person with whom I spent hours talking last night. (more formal)

OR

I hope to hear from the person whom I spent hours talking with last night. (less formal)

Non-restrictive Relative Clauses

This type of relative clause merely provides extra information. This information may be quite interesting and important to the larger conversation, but it is not essential for precise identification of the noun. “That” cannot be used as a relative pronoun in a non-restrictive relative clause. Commas are always used at the beginning and end of this type of relative clause.

A non-restrictive relative clause can modify a single noun, a noun phrase, or an entire proposition.

My mother is thinking of opening a restaurant. My mother is an excellent cook.

“My mother” is already a clearly defined noun, so the second sentence becomes a non-restrictive relative clause set off by commas on both sides.

My mother, who is an excellent cook, is thinking of opening a restaurant.

I’m planning to grow roses. I find roses quite beautiful.

I’m planning to grow roses, which I find quite beautiful.

(not okay) I’m planning to grow roses, that I find quite beautiful.

I’m driving across the country with three small children.

Driving across the country with three small children is going to be stressful.

I’m driving across the country with three small children, which is going to be stressful.

Reducing Relative Clauses

Some types of relative clauses can be “reduced”— the relative pronoun and maybe other words can be removed. You might reduce the clause to make your writing more concise or to add sentence variety. We’ll use the examples above to demonstrate how to reduce both restrictive and non-restrictive clauses.

Restrictive relative clauses can be reduced in two ways.

Subject pronouns can be deleted if –ing is added to the verb.

I like the paintings that hang in the SASB North lobby.

I like the paintings hanging in the SASB North lobby.

Object pronouns can be deleted.

I like the bike that my father gave me.

I like the bike my father gave me.

I hope I hear from the person whom I spent hours talking with last night.

I hope to hear from the person I spent hours talking with last night.

Non-restrictive relative clauses can be reduced in one way.

Subject pronouns with “be” verbs can be deleted in non-restrictive clauses.

I am moving to Louisville, KY, which is home to the Muhammad Ali Museum.

I am moving to Louisville, KY, home to the Muhammad Ali Museum.

My mother, who is an excellent cook, is thinking of opening a restaurant.

My mother, an excellent cook, is thinking of opening a restaurant.

Subject-Verb Agreement in Relative Clauses

Remember that the relative pronoun is substituting for a noun, which could be singular or plural before the substitution. The verb in the relative clause must agree with the original noun.

 People are lucky. People win the lottery.

 People who win the lottery are lucky. (plural verb)

 A person is lucky. She wins the lottery every year.

 A person who wins the lottery every year is lucky. (singular verb)

This can be tricky in “one of the…” constructions. The key is to find which noun the relative pronoun is referring to.

Homelessness is a problem. The problem needs to be addressed.

Homelessness is a problem that needs to be addressed. (singular problem)

Many problems need to be addressed. Homelessness is one of the problems.

Homelessness is one of the problems that need to be addressed. (plural problems)

Sumber : http://writingcenter.unc.edu/handouts/relative-clauses/