A relative pronoun is a type of pronoun that is used to introduce a dependent clause in a sentence and connect it to a noun or pronoun in the main clause. Relative pronouns include words such as "who," "whom," "whose," "which," and "that." They are used to refer back to a noun or pronoun (called the antecedent) mentioned earlier in the sentence and provide additional information about it.

Here are some examples of relative pronouns in sentences:

1. The woman who lives next door is a doctor.

   In this sentence, "who" is the relative pronoun that connects the dependent clause "who lives next door" to the noun "woman."

2. The book that I borrowed from the library is very interesting.

   In this sentence, "that" is the relative pronoun that connects the dependent clause "that I borrowed from the library" to the noun "book."

3. He is the person whose car was stolen.

   In this sentence, "whose" is the relative pronoun that connects the dependent clause "whose car was stolen" to the noun "person."

Relative pronouns allow us to combine multiple pieces of information into a single sentence and make our writing more concise and cohesive.