Linked from
The 36 pages that link to Congruence relation, each with the reason it gives.
Chinese remainder theoremNarrower topic: The theorem is stated entirely in terms of congruences.
Modular exponentiationRelated: It gives the precise meaning of reducing a power modulo the modulus.
Even numberRelated: Even integers form the residue class congruent to 0 modulo 2.
Hilbert's axiomsRelated: Hilbert's congruence axioms govern equality of lengths and angles.