What does U stand for in chemistry?

In chemistry, "U" can stand for a few things depending on the context:

* Uranium: The chemical symbol for the element uranium. It's a radioactive element with the atomic number 92.

* Units: Sometimes "U" is used as a generic symbol for units, particularly in equations or tables.

* Unknown: In some cases, "U" might be used as a placeholder for an unknown substance or value.

If you can provide more context about the situation where you saw "U", I might be able to tell you more specifically what it stands for.