Vocabulary 'beforehand'

Let me try this example: If I had known beforehand you were bringing your friend, I would have prepared more food.

I hope that helps, beforehand is not identical to earlier. I'm not sure right now how to to better explain.....let me think and hopefully I can come up with a better explanation. Oh, it's important to know that your example would be understood by an English speaker, it would just be a little awkward to the ear.

Yes, you used 'beforehand' appropriately and it is not awkward to the ear.
But you don't have to take my word for it since I'm not an english teacher, per se, so we'll just wait till some 'english teacher' bothers to agree with me.

As to the poster above me, I don't know what the hell the person is going on about.

I agree with you, Ice. And, once upon a time, I used to be an English teacher.

Andy, she was not exactly wrong, but if I knew beforehand that this would be a shorts in a knot topic, I would have spent more time working on a more complete explanation.