This document discusses relative clauses, which are dependent clauses that function like adjectives to provide more information about a noun. There are two types of relative clauses: restrictive relative clauses that are necessary for identifying the noun and are not set off by commas, and non-restrictive relative clauses that provide additional information and are set off by commas. Relative clauses can contain who, which, that as subject pronouns or be replaced by participial phrases to make sentences shorter.