Once you have mastered the meanings of the basic parts of speech, the remainder of English grammar is simply a flow-on from those rules. An 'adjective clause' is a subordinate clause that modifies a noun or a pronoun.

1

An adjective clause my begin with a relative pronoun (who, whom, whose, that, and which) or (where and when). An adjective clause normally follows the word it modifies.

Examples: Athletes 'who perform in the Olympics' must spend years in training. Cities 'that host the Olympics' need many athletic facilities. The city 'where the 1996 Summer Olympics took place' was Atlanta.

2

Sometimes the relative pronoun is dropped from the beginning of an adjective clause. Example: The mug 'I use most often' came from those Olympics. [The relative pronoun 'that' has been omitted.]

3

Some adjective clauses are needed to make the meaning of a sentence clear. Such an adjective clause is called an 'essential clause', or a 'restrictive clause'. It must not be set off with commas. Example: Tourists 'who travel to the games' stay in hotels. The living area 'that is designated for the athletes' is called the Olympic Village.

4

An adjective clause that adds information to a sentence but is noit necessary to make the meaning of the sentence clear is called a 'nonessential clause', or 'nonrestrictive clause'. Example: The Columbia Broadcasting System, 'which televised the 1998 Winter Olympics', set up a Website for the athletes.

5

When choosing between 'that' and 'which' to introduce an adjective clause, use 'that to begin an essential clause and 'which' to begin a nonessential clause.