In computing and mathematics, the modulo operation returns the remainder or signed remainder of a division, after one number is divided by another, the latter being called the modulus of the operation.

For example, the expression "5 mod 2" is equal to 1 because 5 divided by 2 has a quotient of 2 and a remainder of 1, while the expression "9 mod 3" equals 0 because 9 divided by 3 has a quotient of 3 and a remainder of 0.