Double
Two Times, Twice, Twofold
noun
Something that is two times is double (or it is just simply two times). Of course, this all works with things like 三倍, 百倍, and 四十二倍 as well.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
二倍にふえる
to increase twofold
二倍にする
to make something double
二倍になる
to double
いつもの二倍の大きさのカップでコーヒーを飲みました。
I had some coffee in a cup that's twice as big as my usual cup.
テレビのボリュームを二倍にしてくれませんか？
Can you double the volume on the TV?
うわ！君のお兄さんって、君の二倍の体重があるんだね！
Wow! Your brother weighs twice as much as you, huh?