noun, noun which may take the genitive case particle 'no'
double; twice as much; twofold
Indicates a quantity, size, or degree that is two times the original. Used as a noun or with の to modify another noun.
今年の売り上げは去年の二倍になった。
This year's sales were double last year's.
この箱はあの箱の二倍の大きさです。
This box is twice as big as that one.
倍 is a suffix meaning '-times' or 'multiplied by', while 二倍 specifically means 'double' or 'two times'.
Compound of 二 (two) and 倍 (times, -fold).