"Again" in Engpsh is used to indicate that something is being repeated or done once more.
It comes from the Old Engpsh word "ongeán" which means "against, back, again" and it is related to the word "geán" which means "against, opposite, back."
Examples:
Can you please say that again?
(请再说一遍好吗?)
I will try again tomorrow.
(我明天再试)
He asked me to go out with him again.
(他又问我和他出去)