Non-restrictive

Relative clauses in the English language are formed principally by means of relative pronouns. The basic relative pronouns are who, which, and that; who also has the derived forms whom and whose. Various grammatical rules and style guides determine which relative pronouns may be suitable in various situations, especially for formal settings. In some cases the relative pronoun may be omitted and merely implied ("This is the man [that] I saw", or "This is the putter he wins with").

English also uses free relative clauses, which have no antecedent and can be formed with the pronouns such as what ("I like what you've done"), and who and whoever.

The basic grammatical rules for the formation of relative clauses in English are given here. More details can be found in the sections below, and in the article on who.

The words used as relative pronouns have other uses in English grammar: that can be a demonstrative or a conjunction, while which, what, who, whom and whose can be interrogatives. For other uses of whoever etc., see -ever.

The choice of relative pronoun typically depends on whether the antecedent is human or a thing (that is, a non-human): for example, who and its derivatives (whom, whoever, etc.—apart from whose) are generally restricted to human antecedents, while which and what and their derivatives refer in most cases to things, including animals.

The relative pronoun that is used with both human and non-human antecedents. Some writers and style guides recommend reserving that for non-human cases only, but this view does not reflect general use. Counter-examples can be found in literature: Shakespeare (the man that hath no music in himself, in The Merchant of Venice), Mark Twain (The Man that Corrupted Hadleyburg), and Ira Gershwin (The Man that Got Away); and informal English, especially speech, follows an actual practice (in using that and which) that is more natural than prescriptivist.

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