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