This is going to be a touchy topic, so hang in there, and we’ll see what we can do with it. Agreement in count is important in English. We don’t say, “He are there,” because ‘he’ is singular and ‘are’ is a plural verb. For the same reason, we don’t say, “Friends is good.” Again, one is plural (‘friends’), the other singular (‘is’).
Agreement between nouns and verbs is good, but nouns and the pronouns referring back to those nouns need to agree as well. In “Lisa is happy because she won the prize,” ‘she’ is referring back to Lisa, so the pronoun agrees with the noun in count (and it also happens to agree in gender, but we don’t care about that now).
The problem is that English doesn’t have a non-gender singular pronoun referring to a person. (The word ‘it’ usually refers to non-people…unless used in a derogatory manner, such as referring to an ex-spouse.)
History:
Part of the problem is that English is such a mishmash of other languages. We took many of our content words (nouns, verbs, adjectives, adverbs, etc.) from Latin, but grammatical words (pronouns, conjunctions, prepositions, etc.) came from other sources, one being Old Norse. The Old Norse pronouns their, theira, theim can be traced back to about 1200, where they replaced the existing words hīe, hīora, him (which could have been confused for the remaining pronouns of ‘he’, ‘her’, and ‘him’).
The plural form of ‘they’ was around for about 100 years before being used to refer to singular subjects, and all was well with the world. For example, in 1375, singular ‘they’ appears in the medieval romance William and the Werewolf. Here’s the Middle English version: ‘Hastely hiȝed eche…þei neyȝþed so neiȝh…þere william & his worþi lef were liand i-fere.’ In modern English, that’s: ‘Each man hurried…till they drew near…where William and his darling were lying together.’
It wasn’t until the Prescriptivists of the 18th century got a hold of English that it was frowned upon “because a plural pronoun can’t take a singular antecedent” (along with a few other ‘rules’ that no longer apply: End of Sentence prepositions and Split Infinitives for example). The Prescriptivists proposed to avoid using plural ‘they’, encompassing singular as well, by using ‘he’, which encompasses females as well—trade one globally misused word for another. They clearly forgot that singular ‘you’ used to be exclusively a plural pronoun. If they had noticed, we would probably still be using ‘thee’ and ‘thou’ for singular second person instead of ‘you’. No one complains about using ‘you’ to refer to a singular subject, so why worry about ‘they’?
Modern:
All right then, enough history. Consider these modern sentences:
- “One of your girlfriends phoned, but she didn’t leave a message.”
- “One of your boyfriends phoned, but he didn’t leave a message.
- “One of your friends phoned, but they didn’t leave a message.”
Any problem with ‘they’ referring to a singular subject? Not if you’re speaking, but written English is a bit more formal…though it is not so formal as to require “he or she” all the time, so relax and converse with your readers.