Uni-
A bike with one wheel
unicycle
A bike with two wheels
bicycle
A bike with three wheels
tricycle
A mythical horse with one horn
unicorn
When you speak two languages you are
bilingual
A shape with 3 sides
triangle
When all the students have to wear the same clothes
uniform
When something occurs twice a week
biweekly
When 3 babies are born at the same time they are
triplets
When everyone sings at the same time they are in
unison
Another word for glasses
bifocals
a group of 3 people
trio
When something is one of a kind
unique
When you cut something in half
bisect
a group of 3 movies
trilogy