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@YCor For instance, $\mathfrak b$, the unbounded number, is the least cardinality of an unbounded subset of $\mathbb N^{\mathbb N}$ under the relation $f\le^* g\Longleftrightarrow \exists n\,\forall m>n\, f(m)\le g(m)$.
@YCor Not the people for which the tag is intended. Yes, we get questions on this site about "algebraic geometry" which are really about finding the equation of a line going through two points whose coordinates are given. This does not mean "algebraic geometry" is a useless tag. Classically, cardinal characteristics or cardinal invariants are cardinals $\kappa$ whose definition implies $\aleph_0<\kappa\le 2^{\aleph_0}$. In practice, they are defined in terms of combinatorial properties.
@YCor No, that sounds crazy. "Cardinal characteristic" is a specific thing with specific meaning. "Large cardinals" means something else. It is like saying that a tag "Euclidean geometry" would encompass "Artificial intelligence".
@YCor No, I think that "small countable cardinals" is too vague in scope to be useful. Cardinal characteristics are specific objects and the examples suggested by Taras seem all to be about them.
I am confused by this comment. Why would one think that small uncountable cardinals is meant to encompass large cardinals? It is the same confusion I feel when reading your proposal. The tag CH is certainly not meant to encompass situations where CH fails.
@Gerry Doesn't everybody? :-) More seriously, though, I think the important bit is that they are informed ahead of time. Whether the moderators decide to wait for a reply or just go ahead with their decision is another matter. I believe that if it can be argued that the post should not be CW, it is still the case that the decision can be reversed (at least, that's how it used to be). But people may feel less comfortable asking for it if the moderators didn't at least try to contact them before proceeding.
