grammar - What is the accepted stance on using "they" in a singular form?

Is it good English to say "They have just left", when talking about a single person (perhaps someone you don't know the gender of)?

(I am a native English speaker, I'm looking for the view held by lexicographers).

Answer

Singular they has been used in English for a long, long time. Seriously, Shakespeare even used it.

Unfortunately, a significant number of English speakers think it's wrong. Why? No clue. I'd label it a hypercorrection.

I think the most important thing to think about is whether your audience will understand you. On this count, singular they really shines, as everybody — even those who pooh-pooh it — understand exactly what you're saying.

Another consideration is what alternatives you have. One sounds stuffy; he or she is too long; just he is inaccurate (and possibly offensive).

Singular they is really the best way to go.