Some time ago I noticed that someone had created , which I find redundant considering the fact that it's usually just , and that it is almost never tagged as such.

Do we really want to save that tag, or can we please please make it a synonym of ?

Thanks to Martin Sleziak's efforts, we no longer have questions under the tag . And as Martin points out below, the uses of this tag were various and not always actually related to cardinals or elementary set theory.

So now we have four general options:

1. Allow the tag to be recreated and let it be.
2. Make the tag synonymous to .
3. Make the tag synonymous to .
4. Blacklist the tag altogether.

Perhaps there are other options, but I'm not sure which ones are worth it. Please voice your opinions in the comments, so we can come to some basic agreement.

(I think that a poll thread with four options is way too much, we should probably narrow it down to two options, or three at most, before posting poll answers.)

• Synonym sounds good to me. – user7530 Oct 22 '13 at 0:05
• There's currently a synonym suggestion to make it a synonym of cardinals. I don't know the area so I couldn't say which suggestion is better. – Dan Rust Oct 22 '13 at 0:24
• I have made this post in the long thread suggesting the synonym with (cardinals) and I've also made the synonym suggestion Daniel mentions. See also this chat transcript. Seeing which questions appeared in this tag since I have suggested the synonym, I agree that elementary-set-theory is probably a better suggestion. (Either retagging them or merging two tags, perhaps even synonimizing the two tags.) – Martin Sleziak Oct 22 '13 at 7:11
• @Martin: I missed that request, as it was in the midst of the conference I attended in Vienna; but it seems that a synonym is probably the way to go. – Asaf Karagila Oct 22 '13 at 7:14
• @Asaf: Even if we make synonym with (cardinals), some (probably most) of the questions having (cardinality) tag at this moment seems more suitable for (elementary-set-theory). Some of them have nothing to do with set theory - for example questions about cardinality of cosets or groups. If I make some retags, I'll make a note in the tagging chatroom. – Martin Sleziak Oct 22 '13 at 7:23
• @Martin: Thanks. – Asaf Karagila Oct 22 '13 at 7:28
• The (cardinality) tag is out of the system. If you want to check whether the questions have retagged correctly, have a look here. But it still makes sense to create some kind of synonym in order to prevent the same problem in the future. – Martin Sleziak Oct 23 '13 at 6:02
• @Martin: So you're not in favor of blacklisting? – Asaf Karagila Oct 23 '13 at 6:03

This is rather a long comment than an answer.

I am personally not in favour of blacklisting outright, which seems like a rather extreme option at this point. (I am open to hear good arguments about this, however.)

From the tag's wiki-excerpt, it does not feel appropriate to make a synonym of this:

This tag is for questions about cardinals and related topics such as cardinal arithmetics, clubs, stationary sets, cofinality, and principles such as $\lozenge$. Do not confuse with [large-cardinals] which is a technical concept about strong axioms of infinity.

This seems to put the focus of on more advanced topics. Heck, I'm not certain if I agree this excerpt, as I think is a much better place for clubs, stationary sets, and $\diamondsuit$ (and $\clubsuit$).

To this end, I would be in favour of the following two-step solution:

1. remove mention of the combinatorial concepts related to cardinals from the tag-wiki excerpt, and at the same time explicitly mention that questions related to the cardinality or equipotence of sets falls under that tag;
2. make a synonym of (and merge, if necessary).
• The combinatorial references were made by me long before Andres came up with the idea to have the infinitary combinatorics tag. I agree with the first step of the two-step solution. – Asaf Karagila Oct 24 '13 at 10:46
• @Asaf: It makes sense that (inf-comb) is much newer (and I was pretty certain you were responsible for the (cards) tag-wiki). – user642796 Oct 24 '13 at 11:27
• @AsafKaragila I have at least removed the combinatorial stuff from the tag-excerpt. – Martin Sleziak Oct 15 '14 at 17:54
• @Martin: Makes sense, now with the infintiary combinatorics tag available. – Asaf Karagila Oct 15 '14 at 17:56