Possible Duplicate:
Is it correct to use “their” instead of “his or her”?
Plural versus singular:
Anyone can learn to dance if they want to.
Anyone can learn to dance if he or she wants to.
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'?
note: this previous posts also says anyone is [singular]: "Anyone has" or "anyone have" seen them?