| A | B |
| unicellular | having only one cell |
| unicorn | a horse-like fabled animal that has one horn growing out of the middle of its forehead |
| unicycle | a one-wheeled vehicle on which the rider sits and pedala |
| unidirectional | moving only in one direction |
| unify | to join together into one group |
| unilateral | one sided |
| unique | one of a kind; unusual or rare |
| unison | an instance of saying the same words or sounds at the same time |
| unit | one group |
| unitard | a one-piece leotard and tights combination |