A prefix is a group of letters that is added to the beginning of a word to form a new word. Like a suffix, a prefix may change the meaning of the word.
The clown is riding on the unicycle .
Animals that have two feet are also called bipeds .
Eugene, Sally and Johnny are triplets .
A quadrangle is a figure with four sides.
An octopus has eight arms.
The side of the bowl is shaped like a semicircle .