Resources online tell me that anyone is a singular indefinite pronoun. Then why is it sometimes acceptable to use the plural 'they' with 'anyone' in some cases? Does it substitute and replace 'he/she'?
Merriam-Webster’s Dictionary of English Usage remarks that “They, their, them have been used continuously in singular reference for about six centuries, and have been disparaged in such use for about two centuries. Now the influence of social forces is making their use even more attractive.”