[English] x times per day or a day

[Jaleel10]

What's the difference between them?

[DaveAgain]

Just two ways of saying the same thing.

[Deinonysus]

I would agree with DaveAgain that there is no difference in meaning.

I would say that there is a difference in formality. If you are speaking with your friends you should use "a day", but if you are writing a business email it might be better to use "per day".

[Jaleel10]

Thanks, guys! I appreciate the responses.

[StringerBell]

I agree with Deinonysus. "a day" is a more colloquial way to say "per day".

I'd be more likely to say "a day" when speaking but "per day" when writing (unless it's an informal message, in which case I'd be equally likely to use either option).

[golyplot]

I'd use "a day" in everything except formal writing.