某某

so-and-so; such and such

1. 如果他们告诉你在某某天来，你不方便就不要答应他们。
   If they tell you to come on such and such a day, don't agree if it's not convenient.
2. 他极少问自己是否喜欢某某人，他只是按照某人是否对自己有用来估价他。
   He seldom asked himself whether he liked such and such a man: he esteemed a man according to whether he was useful to himself.
3. 咱们打个比方吧，有个某某先生来旅馆登记。
   Let's suppose a Mr So-and-so registers at the hotel.
4. 在求职信的开头一定要说明你要求某某工作，理由是 ...
   Always say at the start of an application that you're applying for such-and-such (a job) because ...