An adjective clause gives information about a preceding noun in a sentence. Look at the following examples.
The car that Richie was driving was yellow.
Des Moines, where I live, is in Iowa.
Mr. Creeter, whose brother I know, is the new math teacher.
Like many other adjective clauses, these begin with a relative adjective (which, who, whom, whose,that) or a relative adverb (when or where). When you use a relative clause to describe a noun, make sure to begin it with one of the seven relative adjectives and adverbs listed in the previous sentence.
Adapted from Appendix A, “Writing for Nonnative English Speakers” in Writer’s Handbook v 1.0 used according to Creative Commons CC BY-NC-SA 3.0