They


They is the third-person plural personal pronoun in Modern English. It is also used with singular meaning, sometimes to avoid specifying the gender of the person referred to: see gender neutrality in language.

Special uses

Singular

The singular they is the use of this pronoun as a gender-neutral singular rather than as a plural pronoun. The Oxford Dictionaries have an article on the usage, saying that it dates back to the 14th century.
The singular pronoun they can be found in formal or official texts. For example, a 2008 amendment to the Canadian Criminal Code contains the following text:
if a peace officer has reasonable grounds to believe that, because of their physical condition, a person may be incapable of providing a breath sample... )

In an article published in The New York Times Magazine in 2009, Patricia T. O'Conner and Stewart Kellerman wrote:
Anne Fisher was not only a woman of letters but also a prosperous entrepreneur. She ran a school for young ladies and operated a printing business and a newspaper in Newcastle with her husband, Thomas Slack. In short, she was the last person you would expect to suggest that he should apply to both sexes. But apparently she couldn't get her mind around the idea of using they as a singular.


...

Meanwhile, many great writers — Byron, Austen, Thackeray, Eliot, Dickens, Trollope and more — continued to use they and company as singulars, never mind the grammarians. In fact, so many people now use they in the old singular way that dictionaries and usage guides are taking a critical look at the prohibition against it. R. W. Burchfield, editor of The New Fowler's Modern English Usage, has written that it's only a matter of time before this practice becomes standard English: “The process now seems irreversible.” Merriam-Webster’s Collegiate Dictionary already finds the singular they acceptable “even in literary and formal contexts,” but the Usage Panel of The American Heritage Dictionary of the English Language isn't there yet.

Generic

The pronoun they can also be used to refer to unspecified people in some often vaguely defined group, as in In Japan they drive on the left. or They're putting in a McDonald's across the street from the Target. It often refers to the authorities, or to some perceived powerful group, sometimes sinister: They don't want the public to know the whole truth.

Etymology

In Old English, ' was used as the third-person, personal pronoun. It was gradually replaced by an Old Norse borrowing, ', until it was entirely replaced in around the 15th century in Middle English. Þeir, in turn, became they as it is known in Modern English today. Þeir originates from Proto-Germanic *þai-z, from Proto-Indo-European *toi. By the 18th century the use of "their" - as in the possessive pronoun - was at times interchangeable with the usage of "there". Literature from 1767 has the phrase "...also somewhat otherwise be deduced from their being necessary to support the Honour of God..." which was acceptable. However, by modern Standard English terms, the phrase shows an incorrect use of the possessive pronoun "their", i.e., their being. The appropriate spelling is there being.

Word of the year

In December 2019, Merriam-Webster chose "they" as word of the year for 2019. The word was chosen because "English famously lacks a gender-neutral singular pronoun to correspond neatly with singular pronouns like everyone or someone, and as a consequence they has been used for this purpose for over 600 years."