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 [tag:congruences-and-remainders] as a synonym for [tag:modular-arithmetic];
* Create a [tag:congruence-relations] synonym of [tag:equivalence-relations];
* Create a [tag:geometric-congruence] or [tag:geometric-congruences] synonym for [tag:euclidean-geometry] (I'm not knowledgeable in this area, so I hope someone else can provide a better tag name$^\dagger$);
* Blacklist [tag:congruences].

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$^\dagger$: Martin Sleziak suggested [tag:congruences-geometry] [in the Tagging chatroom](http://chat.stackexchange.com/transcript/message/11944782#11944782).