Two tags can be made synonyms and they can also be merged. What is the difference between these two things?

I am referring here to the terminology used in this post. It contains a list of changes in tags, some of them are marked by m for "merge", some of them are marked by s for "synonym".

I do not know what exactly merging two tags means and what is the difference between this and making the two tags synonyms.

I hope that some more experienced user could explain this. (One of the reason I am asking is to clarify the situation mentioned in this comment. But this is a useful thing to know in general, at least for people who care about correct tagging and try to help with various tag-related issues.)

  • 1
    $\begingroup$ For my part, I have used "merged" and "synonymized" synonymously (mergously?) up until now. $\endgroup$
    – user642796
    Commented Oct 4, 2013 at 7:25

1 Answer 1


Merging and synonyms are two different things. They are not mutually exclusive.

  • Merging (tag1) into (tag2) destroys (tag1) and retags all questions currently tagged with (tag1) as (tag2) instead.

  • Marking (tag1) as a synonym of (tag2) means that

    • Clicking on a link to (tag1) takes you to the page of (tag2)
    • In particular, the two tags share the same tag wiki and so on, and for the purpose of searching the two tags are treated as identical
    • When a user types (tag1) into the tagging field, the software suggests to him to use (tag2) instead. (The user however is free to ignore that and use (tag1). In which case the question will appeared to be tagged as (tag1), even though for all other intents and purposes it behaves as if tagged with (tag2).)

A merging of tags can occur with or without marking the two tags as synonyms. Two tags can be marked as synonyms with or without merging them.

One advantage to synonymising without merging is that in that case the synonym is fully reversible: if some time later we decide that (tag1) should be resurrected and repurposed since it has a technically slight difference from (tag2), we can just undo the synonym and the two tags will exist separately. (Though to be frank I don't think we have yet encountered an instance where this is useful.)

  • $\begingroup$ In the context you linked to, I think when s is used, m is also usually implicit. I think when I started that thread I may not have been aware of the possibility of synonyms without merges. $\endgroup$ Commented Oct 4, 2013 at 7:20

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