Double
Two Times, Twice
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.
にばい
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.
このかぶのかぶかはたったの二日で二倍になった。
This stock's price doubled just in two days.
めんつゆを二倍にうすめるのを忘れないでください。
Don't forget to dilute the noodle soup base two times.
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?