Is it ok to use 'before' at the end of a sentence?

I once had been told by my English teacher that before must be used with a special time or event, like: Say goodbye before you go.

What about:

I've seen that film before.

Is this correct and appropriate? Or is there a better expression?

Solution 1:

In your first sentence, before is a conjunction and, as such, it has to be placed at the start of the subordinate clause which it introduces. In your second sentence, before is an adverb, and it can occur only at the end of that particular sentence.

Solution 2:

That is very common and accepted usage of before. The time is implied (before today/now/etc.).

• I've had mangoes before (today/now).
• Even though I have been to Paris before (that day), it was just as exciting.
• I'm here to find out what you think of Norway. Have you been there before, and what's your opinion about Norway as a destination?

I wouldn't use I've seen that film before in formal writing, however. I would say, I've already seen that film.