UU is the twenty-first letter of the modern Latin alphabet.
Uniform represents the letter U in the NATO phonetic alphabet.
U is also:
- In chemistry, the symbol for uranium
- British novelist Nancy Mitford brought to popular attention the linguistic terminology "U" and "non-U" to indicate the speech markers of upper class and non-upper class British speakers respectively.
- short for "you", used in SMS or instant messages.
- In computer science, 1 U (= 44mm or 1¾ inch) is the unit of the height of computer chassis, also called a rack unit.
- In mathematics, U stands for union, the upside-down ∩ stands for intersection (both are operators for sets)
Two-letter combinations starting with U: