1. A letter is any character that is not considered a number or symbol. For example, 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, and z are all letters in the English language and letter keys on the keyboard.
2. Letter also describes a paper format, see the A4 definition for further information on this term.
3. Lettering is the process of inscribing letters onto or into something. For example, inscribing letters into wood or embroidery letters are both examples of lettering.
4. A letter describes a message from one person to one or more other people.