noun, noun which may take the genitive case particle 'no'
four times; quadruple; fourfold
Indicates a quantity or degree that is four times as much as a reference. Used as a noun or with の to modify another noun.
今年の売上は去年の四倍になった。
This year's sales became four times last year's.
四倍の量の水を加えてください。
Please add four times the amount of water.
倍 is the general counter for 'times' or '-fold'; 四倍 specifically means 'four times'.
二倍 means 'double' or 'two times', while 四倍 is 'quadruple' or 'four times'.
Compound of 四 (four) and 倍 (times, -fold).