* Unicycle: a cycle with one wheel.
* Unilateral: relating to or affecting only one side.
* Uniform: the same in all parts or aspects.
* Unique: being the only one of its kind.
* Unify: to make into one unit or whole.
* Universe: all existing matter and space considered as a whole.
* Unison: occurring at the same time or in the same way.
* United: joined together as one.
Let me know if you'd like more examples!