1. RELATIVE CLAUSE

2. Introduction
A relative clause is a dependent clause that functions as an adjective; that is, it modifies a noun or pronoun. For this reason, relative clauses are also called adjective clauses.
The first American thanksgiving feast, which took place in 1621, lasted three days.
Everyone who studied for the exam passed it easily.

3. Relative Pronoun and Relative Adverb

4. Position of Relative Clauses
Compare the following sentences:
He left the gift in his friend’s car that he had just bought.
He left the gift that he had just bought in his friend’s car.

5. Verb Agreement in Relative Clauses
The verb in a relative clause should agree in number with its antecedent. Compare:
A person who works part-time usually receives no benefit.
People who work part-time usually receive no benefits.

6. Punctuation of Relative Clauses
Relative clauses are either restrictive (necessary) or nonrestrictive (unnecessary). A restrictive clause is necessary because it identifies its antecedent for the reader. Do not use commas with restrictive clauses.
The professor who teaches my biology class won Nobel Prize two years ago.
Professor Jones, who teaches my biology class, won Nobel Prize.

7. Relative Pronoun as Subject
Football, which is the most popular American sport, began at Harvard University.
People who/use use microwave ovens save time and energy.
Ovens that use microwave energy are capable of cooking foods quickly.

8. Attention!
Use either who or that if the relative clause is restrictive, while you can use merely who if it is nonrestrictive (For humans).
Use that if the relative clause is restrictive and which if it is not restrictive (for non humans/things)

9. Relative Pronouns as Objects
The address that he gave me was incorrect.
The professor whom/that/X you should see is chair of English Department.
Dr. White, whom you met in my office, is my uncle.
The book that/X the professor translated was written in German.
Phonology, which Mr. Andrew teaches, is the most difficult course in college.

10. Attention!
If the clause is necessary, use whom, that or no relative pronoun (represented by X), while you can use whom if it is not necessary (for humans).
If the clause is restrictive, that and no relative pronoun can be used, while if it is nonrestrictive, you can use which.

11. Exercise
Make five sentences where the relative pronouns become subject (two for restrictive and three for nonrestrictive).
Make five sentences where the relative pronouns become object (two for restrictive and three for nonrestrictive).