"We will note that 'they' has been in consistent use as a singular pronoun since the late 1300s; that the development of singular 'they' mirrors the development of the singular 'you' from the plural 'you'" noted M-W on its blog, "yet we don't complain that singular 'you' is ungrammatical." " The Guardian
SOURCE: ArtsJournal at 10:06AM on September 18, 2019