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.