Integers a and b for which the difference is a multiple of the number n.
We also say that a and b are congruent modulo n if they have the same remainder after division by n.
Examples
- The numbers 9 and 21 are congruent modulo 12, as we can see in the notation system for hours modulo 12, 21 hours corresponds to 9 o’clock at night.
- The numbers 25 and 45 are congruent modulo 10 because their difference, which is 45 – 25 = 20, is a multiple of 10.