For anyone who cares about English grammar, the news will resolve an issue that has proved to be insoluble forever. Merriam-Webster has announced that henceforth the pronoun they may be used to refer to a “single person whose gender identity is nonbinary.” This no doubt applies to their as a substitute for his or her.
According to Benjamin Dreyer in “Dreyer’s English” this issue has been a pebble in the shoes of grammarians as far back as the 13th Century. It arises in a sentence, “A student should be able to study whatever [he/she/they] likes.”
To use he or she is gender-limiting, and to use they, which until now has always been a plural pronoun, is improper because it is a plural reference to a singular pronoun. This has been the “ruling” in spite of the fact that in spoken use for eons they has been commonly (and improperly) used by speakers who don’t think twice about it.
Unfortunately, until now efforts to solve the problem have all floundered. You will often see, “A student should be able to study whatever he/she likes.” As cumbersome as that may be in writing, it is even more so in spoken use. I have used he or she (as in “A student should be able to study whatever he or she likes.”), which is a bit less cumbersome, but not ideal. Some will use it (in lieu of he or she), but that fails because it refers to something which does not have a gender identity.
Some decades back a “sensible” solution was offered in the form of new, gender-neutral pronouns ne (for he or she) and ner (for his or her). Nice logical solution that obviously arrived stillborn. (Who remembers Esperanto?)
Before surrendering totally, let me observe that there is an easy, sensible construction that will win the approval of all grammarians. It is simply to make the subject of the sentence plural: “Students should be able to study whatever they like”. A writer can almost always tailor his or her sentence to make it plural. No bending of the rules; nor is it cumbersome. They is used in its traditional, plural sense. But as readily available as it may be, it is largely ignored as an alternative.
The singular they rules!
— Ken Butera