Bi- means two

bicolor (adj) - having two different colors

bicuspid (n) - a two-pointed tooth located in the side of the jaw

bicycle (n) -   a vehicle with two wheels

biennial (adj) - happening every two years

bifocals (n) - eyeglasses with lenses that have two different sections - for seeing up close and far away

bilingual (adj) - able to speak two different languages

bimonthly (adj) - happening every two months

biped (n) - a two-footed creature

biplane (n) - an airplane with two pairs of wings

biweekly (adj) - happening every two weeks