• 倍ばい — times / double
• 二倍にばい — twice / two times
• 倍増ばいぞう — double increase
• 倍率ばいりつ — magnification rate
• 倍加ばいか — doubling / increase

倍 is composed of the radical 亻 (にんべん) indicating a person, and the right side, 咅, provides the sound. It originally referred to someone who stands in place of another — hence "double" or "multiple". Today, it's widely used to express multiplication or comparison.