Modulus

The modulus function provides the remainder of division. For example, in 5 / 3 the remainder is 2. This is often restated as "5 is congruent to 3 modulo 2" and written symbolically as "<math>5 \equiv 2 \mod 3</math>". Similarly, we could write <math>19 \equiv 1 \mod 3</math> to express the remained of carrying out this division.

Unrelatedly, the complex analogue of the absolute value, given by <math> |a+bi| = a^2 + b^2</math> is also sometimes known as the modulus.