There seems to be considerable support for taking on this tag (+8/-0), which is "high", for questions about tagging).
This answer intends to poll the specific approach I suggested.
Concretely, I suggest to:
- Introduce congruences-and-remainders as a synonym for modular-arithmetic;
- Create a congruence-relations synonym of equivalence-relations;
- Create a geometric-congruence or geometric-congruences synonym for euclidean-geometry (I'm not knowledgeable in this area, so I hope someone else can provide a better tag name$^\dagger$);
- Blacklist congruences.