Final answer:
A relative clause is a dependent clause that modifies a noun or pronoun and typically begins with relative pronouns like 'who', 'whom', 'whose', 'which', or 'that'. They provide additional information and can be essential (restrictive) or non-essential (nonrestrictive) to the sentence.
Step-by-step explanation:
Understanding Relative Clauses
A relative clause is a type of dependent clause that modifies a noun or pronoun in the main clause of a sentence. This means it cannot stand alone and does not express a complete thought without being attached to an independent clause. Relative clauses typically start with relative pronouns such as 'who', 'whom', 'whose', 'which', and 'that'. These pronouns are used to connect the clause to the noun or pronoun it is modifying, providing additional information about the subject.
For example, in the sentence 'The book that I lent you is overdue,' 'that I lent you' is a relative clause modifying 'The book'. The subject in this clause is 'I', and the verb is 'lent'. Relative clauses can be restrictive (essential) or nonrestrictive (non-essential). A restrictive relative clause provides essential information about the noun being described and does not use commas. Meanwhile, a nonrestrictive relative clause adds extra information that isn't necessary to understand the sentence and is usually enclosed in commas.