There was some agitation on Twitter this week (Imagine!) when a gentleman named Andy Smarick took exception to a tweet from @MerriamWebster that used singular their. He tweeted, “The singular they is an affront to grammar. Language rules are all that separates us from animals. We. Must. Stand. Firm.”*
Singular they was common and unremarkable in English for centuries until eighteenth- and nineteenth-century grammarians decided that the language would be tidier if it were limited to the plural. But it has endured nevertheless, including among reputable writers, as the entry in Merriam-Webster’s Dictionary of English Usage amply demonstrates. And though singular they has been in exile from standard English, it has been following the rules for pronouns in nonstandard usage. Moreover, it is increasingly appearing without remark in published, edited prose.
The entry in the Oxford English Dictionary for this usage says simply: “Often used in reference to a singular noun made universal by every, any, no, etc., or applicable to one of either sex (= ‘he or she’).” No disparaging label is attached.
The point that has eluded Mr. Smarick is this: We make the rules. Language is not an entity separate from and above us; it is what we collectively make it.
If Mr. Smarick is distressed to learn that the OED countenances singular they, he will be in danger of an apoplexy to hear that it also includes in its latest intake bovvered, tl;dr, LMFAO, and sleeping with the fishes.
People who fume over these entries misunderstand how dictionaries work, and particularly what the OED intends. The OED operates under the staggering ambition to make a complete historical record of the English language. It includes words that no one has used for centuries, in that regard resembling an attic full of broken furniture and old rope. Similarly, if these current usages should mount, shine, evaporate, and fall, the OED will preserve them so that a reader coming across them for the first time can look them up to find their meaning, their derivation, and the place and time of their use. That is what dictionaries are for, not to serve as an honor roll for words.
*It is hard to resist the temptation to be pedantic with a pedant. Though all in his second sentence can be construed as a singular (“All is lost”), that it is the predicate complement of rules suggests that a plural verb would be less jarring. Also, the fad of separating each word in a sentence with a full stop for emphasis (perhaps derived from Comic Book Guy on The Simpsons: “Worst. (Noun.] Ever.”) has grown stale.