もうAlready, Anymore

In English, もう is regularly translated to 'already', or 'anymore', depending on if it is used in a positive-past (already), or negative (anymore) sentence. The reason that Japanese only requires one word for both of these nuances is due to もう literally meaning 'something has unexpectedly ended'.

From these sentences we can see that もう can be translated in each case as the following.

(Past) - Although expected to not be done, it is. 'Already', in English.

(Negative) - Although expected to still be going, it isn't. 'Anymore', in English.

This is the opposite of まだ, which means 'something is unexpectedly still going'.

もう may also be used to ask questions. This is when the speaker thinks that something 'might' have ended, but wants to confirm.

Fun Fact

もう is often used simply as an expression of exasperation (giving up on arguing), to show that someone has already reached the point of not wanting to continue.