A clause is a group of related words which has both a subject and a predicate. A clause is different from a phrase because a phrase is a group of related words which lacks either a subject or a predicate or both. Adjective clauses modify nouns or pronouns . An adjective clause nearly always appears immediately following the noun or pronoun. To test for adjective clauses there are a couple questions that you can ask.
Most adjective clauses begin with who, whom, which or that .
Sometimes the word may be understood. In other words, the words that or who , for example, would not specifically be in the sentence, but they would be implied. Occasionally, an adjective clause is introduced by a relative adverb, usually when, where or why . Adverb clauses usually modify verbs, in which case they may appear anywhere in a sentence. They tell why, where, under what conditions , or to what degree the action occurred or situation existed.