it is a kind of mathematical game that of a consists of mathematical equation among unknown numbers, whose digits are represented by letters. The aim is to identify the value of each letter.

a good example is the skeletal division cryptarithm, 9567 + 1085 = 10652 which can be represented like this:

abcd + efgb = efcbh famous eg:- S E N D 9 5 6 7 + M O R E 1 0 8 5 = M O N E Y 1 0 6 5 2