A set (usually of letters) from which a subset is drawn. A sequence of letters is called a word, and a set of words is called a code.
Alphabet
See also
Code, String, WordExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Alphabet." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Alphabet.html