Translation guide
The English word "twice" means two times. In Japanese, the most common way to express this is with the counter 二回 (にかい), but other expressions exist depending on context, such as doubling or doing something again.
Expressing that an action or event occurs two times.
The standard counter for occurrences. Use with a verb to say 'do something twice'.
I go to the gym twice a week.
I've seen that movie twice.
Similar to 二回, but slightly more formal or literary. Often used in set phrases.
Please don't do that ever again. (lit. 'don't do that twice')
Expressing that something is twice as much or twice the amount.
Means 'double' or 'twice as much'. Used for quantities, sizes, etc.
He earns twice my salary.
This room is twice as large as that one.
Expressing that something is done again, or for a second time.
Expressing frequency over a time period.
Pattern: time period + に + 二回. E.g., 一日に二回 (twice a day).
I brush my teeth twice a day.
Both mean 'twice', but 二回 is more common in everyday speech. 二度 is often used in negative sentences like 二度と〜ない (never again).
When 'twice' means 'double the amount', use 二倍, not 二回. Saying 二回の給料 would mean 'salary of two times' (as in occurrences), which is unnatural.
I've been to Japan twice.
This costs twice as much as that.
Please check again (a second time).