"They" is sometimes used as a
third-person singular gender-neutral pronoun. Some grammar
mavens may disagree, and consider the construct to be
vulgar. Other insist that concern over using "they" in a singular context is
pedantry. Some even consider the condemnation utterly incorrect as most
grammarians who denounce the use of "they" in the singular are basing their judgement on the rules of the
Latin language.
In any case, the lack of a widely accepted, formal set of gender-neutral pronouns poses a significant burden on the English writer. The use of "one," "he or she," or "he/she" are often awkward, particulary when they are used repeatedly. "It," when applied to a person is dehumanizing, and the classic form, "he," is often seen as sexist as well as being awkward in some situations. Many notable writers simply fall back on the commonly used "they."
Besides the Oxford English Dictionary, and the King James Bible, the use of "they" in the singular appears in the works of the following authors (compiled by Henry Churchyard):
Geoffrey Chaucer, Edmund Spenser, William Shakespeare, Jonathan Swift, Daniel Defoe, Frances Sheridan, Oliver Goldsmith, Henry Fielding, Maria Edgeworth, Percy Shelley, Lord Byron, William Makepeace Thackeray, Sir Walter Scott, George Eliot (Mary Anne Evans), Charles Dickens, Mrs. Gaskell Anthony Trollope, John Ruskin, Robert Louis Stevenson, Walt Whitman, George Bernard Shaw, Lewis Carroll, Oscar Wilde, Rudyard Kipling, H. G. Wells, F. Scott Fitzgerald, Edith Wharton, W. H. Auden, Lord Dunsany, George Orwell, and C. S. Lewis.