[bradleyjg]

There are at least three different usages of singular they. The newest is where a specific person for various possible reasons has asked to be referred to in that way. The oldest usage is where the referent is unknown or generic. E.g. "The technician sent by the company isn't here yet, they may have gotten stuck in a traffic." Finally, some people use singular they even where the referent is specified and that person hasn't expressed a preference for singular they. E.g. "President Obama is on vacation, they must be tired after dealing with ISIS all last week." I find this last usage jarring.