Tra từ again - Từ điển Oxford Advanced Learner 8th

again BrE [əˈɡen] NAmE [əˈɡen] BrE [əˈɡeɪn] NAmE [əˈɡeɪn] adverb
1. one more time; on another occasion
• Could you say it again, please?
• When will I see you again?
•This must never happen again.
•Once again (= as had happened several times before), the train was late.
•I've told you again and again (= many times) not to do that.
•I'll have to write it all over again (= again from the beginning).
2. showing that sb/sth is in the same place or state that they were in originally
• He was glad to be home again.
• She spends two hours a day getting to work and back again.
•You'll soon feel well again.
3. added to an amount that is already there
•The cost is about half as much again as it was two years ago.
•I'd like the same again (= the same amount or the same thing).
4. used to show that a comment or fact is connected with what you have just said
•And again, we must think of the cost.
5. then/there ~ used to introduce a fact or an opinion that contrasts with what you have just said
•We might buy it but then again we might not.
6. used when you ask sb to tell you sth or repeat sth that you think they have told you already
•What was the name again?
see (every) now and again/then at ↑now _adv., (the) same again at ↑same _pron., time and (time) again at ↑time _n.

Word Origin:
[again] Old English ongēan, ongægn, etc., of Germanic origin; related to German entgegen ‘opposite’.