word choice - When to use "nowhere" and when "not anywhere"

What is the difference between "nowhere" and "not anywhere"; both means the same thing, I guess. Is one of them more polite or more formal?

What is the defining factor to decide which one to use?

Answer

Nowhere would be the normal usage. However, it might be appropriate if you had done a search of a house for something or someone, to shake your head in despair, and say "It's not anywhere". The implication is that you have looked everywhere, and it is not in any of the places you have looked.

It is slightly idiomatic, though, so it is not for use in formal writing.