Nouns:
* Umbrella: A portable canopy used for protection from rain.
* Unicorn: A mythical creature with a single spiral horn on its forehead.
* Underwear: Clothing worn under other clothes.
* Universe: All existing matter and space.
* Upheaval: A violent or sudden change or disruption.
* Usage: The way in which something is used.
* Utility: The state of being useful.
* Utopia: An imagined place or state of things in which everything is perfect.
Verbs:
* Understand: To grasp the meaning of something.
* Unleash: To release or let loose.
* Unwrap: To remove the covering from something.
* Uplift: To raise or improve something.
* Utilize: To use something for a particular purpose.
* Undermine: To weaken or destroy something gradually.
* Unite: To join together or become one.
Adjectives:
* Unbelievable: Too extraordinary to be believed.
* Unusual: Not common or ordinary.
* Unhappy: Feeling or showing sadness.
* Ugly: Unpleasant to look at.
* Uncertain: Not sure or definite.
* Ultimate: The most extreme or final.
* Upright: Vertical or erect.
* Useful: Having a practical purpose.
This is just a small sample; there are many other nouns, verbs, and adjectives that start with the letter "u." You can find many more examples in dictionaries and online resources.