one or the other of two; it does not matter which

The offices on either side were empty.

There's a door at either end of the corridor.

used after negative phrases to state that a feeling or situation is similar to one already mentioned

Well, I think she's either Czech or Slovak.

I'm going to buy either the blue one or the red one—I can't decide.

Either he could not come or he did not want to.

used to add extra information to a statement

I know a good Italian restaurant. It's not far from here, either.

LEARNit Dictionary