From NPR Fresh Air
By Geoff Nunberg
Letter-for-letter, no part of speech gets people more worked up than pronouns do. Linguistic history is dotted with eruptions of pronoun rage. Right now, the provocation is the gender-neutral pronouns that some nonbinary people have asked to be called by, so that they won't have to be identified as "he" or "she."
There are several of these in circulation. Some are new words, like "ze" and "co," but some go back a ways — in fact, people have been proposing new gender-neutral pronouns for 150 years, though none has ever caught on. But the most popular choice, and probably the most controversial one, is the familiar pronoun that people describe as the singular "they."
You can see why people would pick "they." In everyday speech we often use that pronoun for a single person, though only when the word or phrase it substitutes for — its antecedent, as it's called — doesn't refer to a specific individual. So we say, "Somebody lost their wallet," or, "If a student fails, they have to retake the course." Or the person we're referring to may be simply unknown. Your daughter's cell phone rings at the dinner table; you say, "Tell them you'll call them back." Male or female, one caller or several? The pronoun "they" is like, "whatever..."
Geoffrey Nunberg is a linguist, researcher, and adjunct professor at the UC Berkeley School of Information, and a regular contributor on NPR’s Fresh Air.