# On the [gcd] tag

Some couple of days ago, some question was bumped and it had spawned (apparently in its original version) a tag named .

I find this tag to be particularly uninteresting, and somewhat non-revealing on the contents of the question. I removed that tag.

Now I see that there are suddenly two questions tagged , and I wonder what the course of action should be. If I remove it, I am running the risk that tomorrow there will be four questions, removing those may cause 16 questions appear, and removing those may cause 256* question appear, which would be an overall insane amount of edit wars going on.

Seeing how I don't have the time to partake in a global edit war which will last for about a week before all the questions on the site are tagged , or at least touched by edits related to this tag, I decided to bring the issue to meta.

We can debate about it for a few days, take a poll if necessary, and see what happens.

EDIT (Oct. 2nd) The tag has already 13 questions, meaning manual deletion is no longer a one-time hit.

I think that there's enough support here to make the tag a synonym of , or remove it completely (and hope it doesn't come back anytime soon).

• To calculate the number of questions in the tag I am using the following formula: $q_{n+1}=2^{q_n}$, where $q_0=0$.
• Possible ways of dealing with this, as I see, are either removing it again; adding a synonym of elementary-number-theory; or allowing it to grow and take over the entire site (or not). – Asaf Karagila Sep 18 '13 at 7:20
• Hmm. Elementary number theory deals with (AFAICT) the ring of integers only, but gcds exist in other rings as well (e.g. rings of polynomials). Granted, if this tag becomes popular, the vast majority of questions tagged with it will deal with integers only. Therefore I'm not sure that adding a synoym of elementary-number-theory is an ideal solution. But I'm not sure that the tag is useful and/or needed either! We have been doing quite well without. – Jyrki Lahtonen Sep 18 '13 at 7:30
• I've mentioned thin in chat, but since there were no questions in that tag at that time, we did not discussed it in the end. (It was after you removed the first question and before the two new questions were added to that tag.) – Martin Sleziak Sep 18 '13 at 7:36
• @JyrkiLahtonen I'd guess that questions about gcd of polynomials will not be negligible, if we keep the tag. (Gcd of integers and of polynomials are two topics that are, in my opinion, most probable to appear in homework and homework questions are quite substantial part of the bulk of questions asked on this site.) – Martin Sleziak Sep 18 '13 at 7:41
• My take: Remove it, and if it gets back too often, synonymize it with (elementary-number-theory). (Hm. GCD of polynomials is a good point. May need to reconsider.) – Lord_Farin Sep 18 '13 at 7:42
• Unrelated: why is it that \$\gcd\$ yields $\gcd$ and \$\lcm\$ yields $\lcm$? – Git Gud Sep 18 '13 at 16:30
• [divisibility] may be the closest populated tag. – zyx Sep 18 '13 at 22:58
• A good idea, zyx! Admittedly I haven't looked at the questions carryig the divisibility-tag. Will do so now. – Jyrki Lahtonen Sep 19 '13 at 5:38
• Quick sampling of questions with divisibility tag surprised me with the absence of questions related to divisibility of polynomials. I guess questions about divisibility of polynomials often appear in either algebra-precalculus or in a more abstract context. – Jyrki Lahtonen Sep 19 '13 at 5:46
• Maybe a stupid question, but is there a basic reason to want to limit the number of tags? I think that having tags that apply to a specific sub-area of another tag could often help searching (provided of couse that relevant questions are so tagged). What would be neceesary then is to forbid certain tags to be the unique one used for a question. Would that be a reasonable feature? – Marc van Leeuwen Sep 19 '13 at 12:39
• @GitGud: You should ask Knuth. There are $32$ names predefined in plain $\TeX$: $\arccos$, $\arcsin$, $\arctan$, $\arg$, $\cos$, $\cosh$, $\cot$, $\coth$, $\csc$, $\deg$, $\det$, $\dim$, $\exp$, $\gcd$, $\hom$, $\inf$, $\ker$, $\lg$, $\lim$, $\liminf$, $\limsup$, $\ln$, $\log$, $\max$, $\min$, $\Pr$, $\sec$, $\sin$, $\sinh$, $\tan$, $\tanh$ ($\TeX$book, page 162). I think nobody ever dared/cared to extend this list. – Marc van Leeuwen Sep 19 '13 at 12:46
• @Marc: There is a five tags limit on a given question. Then you have people who are confused about which tags to use, and they just stick a bunch of arbitrary tags (usually [logic], because you know... it requires some logical brain to solve the problem!) and that's bad. If the tagging system is nicely done, then it is at least easier to re-tag after these users. – Asaf Karagila Sep 19 '13 at 16:22
• Now someone created also (gcd-lcm). I'd say that if we keep (gcd), this new tag should be a synonym. – Martin Sleziak Sep 25 '13 at 12:14
• Probably lcm as well, @Martin. – Asaf Karagila Sep 25 '13 at 14:41
• gcd and been merged into and made a synonym of divisibility. Accepting dfeuer's answer below should end this discussion. – user642796 Oct 6 '13 at 4:44

As zyx sort of suggested, making this a synonym for looks like a good plan.

Edit: As this seems to be a reasonably popular approach, does anyone with the power to propose this tag synonym wish to do so?

If it is determined to be a bad tag, just remove it from all questions and wait for the daily script to delete the tag.

If it is shown to be unkillable and is revived again, ask the moderators to have SE blacklist the tag.

I don't think this tag is useful, and should be removed (and no longer be used).

I'm posting this answer to determine if the community wants this tag removed, so upvote if you agree, downvote if you disagree. ;)

The tag can be useful. It would concentrate under the same tag questions about gcd of integers, polynomials and also more general questions about greatest common divisor in commutative rings.

• Just providing something to upvote for user whose opinion differs from the answers posted so far. (And, of course, something to downvote for those who disagree with this post.) As far as I am concerned, I am rather indifferent - I don't have strong preference one way or another. – Martin Sleziak Sep 19 '13 at 6:19
• Amusingly there are three people who think this is a useful tag, but at most one of them bothered to downvote anorton's answer. – Asaf Karagila Oct 2 '13 at 8:43