U

upside down = in the opposite direction of up

This monkey prefers hanging upside down to sitting on the branch.

b. up to = the responsibility of a decision belong to someone.

Most of the really important decisions to be made are left up to his boss.

a. used to = something is in the past–similar to "did."

I used to eat a lot of candy, but now I don’t because it’s bad for my teeth.

b. used to = accustomed to something; in the habit of.

I’m used to eating healthy food, whether it tastes good or not. (a gerund often appears after "used to.")

Are you used to your computer, or is it difficult to operate?

 use up – use all of something; deplete food.

We’re going to use up all the milk and the eggs when we make lunch, so we need to get some more.