I now noticed that there is a separate tag for schauder-basis.

Another tag containing the word basis in its name is groebner-basis.

Here is an example of a question where the OP used schauder-basis, but the question is clearly about the basis of a vector space.

So even if we later decide that the tag basis is not needed as a separate tag, it might still be useful to have it at least as a synonym. (So that inexperienced users do not use other tags containing this word but completely unrelated to topic at hand.)

I have bumped the thread about synonym between fractions and rational-numbers by adding two poll answers:

I understand that whatever the moderators do, it could be considered as overriding community decision.

The synonym was created by users voting on the tag-synonym. So it is a community decision.

If enough users vote to say that they should not be synonyms, then it is also a voice of community.

So the decision whether mods should remove the synonym is not entirely simple.

Not to mention that we do not really know what exactly happens if a tag-synonym is is removed: meta.math.stackexchange.com/questions/20778/…

Jyrki confirmed, that moderators know about this.

And he later unconfirmed it: