Only when written 早く
Used for something happening earlier than expected or before a deadline. Also used as a noun in expressions like 早くに.
I have to get up early tomorrow.
早く帰ってきてね。
Come home soon, okay?
I have to get up early tomorrow.
Please hurry, or we'll be late.
I was tired, so I went to bed early.
He runs the fastest in the class.
I arrived at the station early, so I waited a bit.
I want to finish my homework quickly and go play.
at the earliest; at the soonest