Generally speaking, the term alphanumeric refers to anything that consists of only letters and numbers. For example, "ABC123" is an alphanumeric expression. The term may also refer to a device that handles such expressions (contrary to letters-only or numbers-only processing equipment). In telecommunication and computer science, an alphanumeric entity is specifically defined as a character string that contains only letters and digits (and sometimes a few other characters, typically punctuation marks).

See also: ASCII