--noun

1. cipher: a mathematical element that when added to another number yields the same number.

--adj.

2. indicating the absence of any or all units under consideration.

0 is both a number and the numerical digit used to represent that number in numerals. The number 0 fulfills a central role in mathematics as the additive identity of the integers, real numbers, and many other algebraic structures. As a digit, 0 is used as a placeholder in place value systems.