1. What is an adjective Clause?
An adjective clause is a dependent clause which takes the place of an adjective in another clause or phrase. Like an adjective, an adjective clause modifies a noun or pronoun, answering questions like "which?" or "what kind of?" Consider the following examples:
Adjective
the red coat
Adjective clause
the coat which I bought yesterday
Like the word "red" in the first example, the dependent clause "which I bought yesterday" in the second example modifies the noun "coat." Note that an adjective clause usually comes after what it modifies, while an adjective usually comes before.
In formal writing, an adjective clause begins with the relative pronouns "who(m)," "that," or "which." In informal writing or speech, you may leave out the relative pronoun when it is not the subject of the adjective clause, but you should usually include the relative pronoun in formal, academic writing:
informal
The books people read were mainly religious.
formal
The books that people read were mainly religious.