A pronoun that introduces an adjective clause. The relative pronouns are which, that, who, whom, whose. Who and whom refer only to people. Which refers to things, qualities, and ideas--never to people. That and whose refer to people, things, qualities, and ideas. See also: Subordination with Adjective Clauses.
Examples and Observations:
- "How can you govern a country which has 246 varieties of cheese?"
(Charles De Gaulle) - "On the plus side, death is one of the few things that can be done just as easily lying down."
(Woody Allen) - "An atheist is a man who has no invisible means of support."
(John Buchan) - "Even if you do learn to speak correct English, whom are you going to speak it to?"
(Clarence Darrow) - "Never play cards with a man called Doc. Never eat at a place called Mom's. Never sleep with a woman whose troubles are worse than your own."
(Nelson Algren) - "Three relative pronouns stand out as being particularly common in English: who, which, and that. The zero relativizer [or dropped relative pronoun] is also relatively common. However, . . . the relative pronouns are used in very different ways across registers. For example:
- That and zero are the preferred choices in conversation, although relative clauses are generally rare in that register.
- Fiction is similar to conversation in its preference for that.
- In contrast, news shows a much stronger preference for which and who, and academic prose strongly prefers which.
(Douglas Biber, Susan Conrad, and Geoffrey Leech, Longman Student Grammar of Spoken and Written English, Pearson, 2002)

