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12:58 AM
@YCor You can check out the overview of tag-related terminology I wrote at the end of this post: What to do with the synonyms for the deprecated tags?
It seems to me that what you mean is merging. When moderators merge tag A into tag B, that also replaces all instances of tag A by tag B.
> Merging two tags. Merging should be used carefully, since it is not a reversible process. If a tag (geometry) is merged into (mg.metric-geometry), that means that all instances of (geometry) are changed to (mg.metric-geometry). (Without bumping any questions.) The change is also made in the revision history. (So from the question it will no longer be visible which tag it had before merging.)
> There is a section "What are merged tags?" in the FAQ post: What are tag synonyms and merged tags? How do they work?
Of course, the tag would have to be created first - but that's bumping just one post.
As I wrote above, merging is not reversible - so one should be careful with this operation.
Merging can be done both with and without a synonym.
In this specific case, if is going to be replaced by , my opinion would be that it is better to keep the synonym. (So that if somebody starts typing "peano" in the tag field, this tag is offered.)
For similar reasons I have suggested a synonym between and some time ago. (Although the mods probably decided against it - judging from the fact that my post was deleted by a mod.)
The explanation I got here also helped me understand merging a bit better: What happens with the tagged questions when a tag-synonym is cancelled?
I remember merging being used several times on Mathematics - when some tag was being cleaned up, if all remaining occurrences fit into some other tag, a moderator simply merged them; this had an effect that a tag was removed without bumping any questions.
For example here: The was merged into . In that way, this tag was removed without bumping any questions.
 
 
7 hours later…
8:09 AM
In fact, I could have simply linked to this conversation for the example with : chat.stackexchange.com/rooms/3740/conversation/…
 
 
11 hours later…
7:13 PM
yesterday, by YCor
(...) One such operation (a) is to make A a synonym of B. In such an event, every future use of tag B is automatically "replaced" with A. This has been done in many cases. Is there an operation (already performed?) (b) in which, as a result, tag A is reset to 0? that is, allowing future uses of tag A, or future (= posterior to operation) manual addition of tag A to questions with tag B? or any other variant (still with the immediate effect of making tag A at least apparently disappear)?
Just to clarify, if you really want to tag A disappear, that would be merging without a synonym.
This was done on MO many times - with merging into .
As I have mentioned, to me this seems a bit non-standard way to get rid of the tag: Burnination vs. merging into a specific tag. (But MO moderators seem to prefer doing it this way.)
 

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