- bisTwice; showing that something is, or is to be, repeated, such as a passage of music, or an item in accounts.
- besaielA great-grandfather.
- biflorousBearing two flowers or blooms.
- bimembralHaving two members.
- binomenA name having two parts.
- bipinnariaThe larva of certain starfishes as developed in the free-swimming stage.
- bisexousBisexual, hermaphroditic (having both male and female parts or functions).