When should I use apostrophe?

[cccheng]

For example, should it be manager's room or manager room ?

Thanks in advance,
Vincent

[konungursvia]

It's hard to know. But we don't call it the manager's room, although in HK "room" is used for office a lot. I'd call it the Manager's Office.

[TheParser]

For example, should it be manager's room or manager room ?

Thanks in advance,
Vincent

ATTENTION: NOT A TEACHER


Tom: Your wife has come to talk with you about an emergency.

Joe: What's wrong?

Tom: I don't know.

Joe: Where is she?

Tom: She's waiting for you in the manager's office (the office of the manager).