U

U is the twenty-first letter of the modern Latin alphabet.

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

U was originally a capital letter like J and it was only Pierre de la Ram�e who made the distinction between capital and small letter. See V.

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 1� 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)