If a person is only interested in number theory, then he/she would just want to access only a few tags, such as number theory, elementary number theory, diophantine equation, etc. But if we select both “number-theory” and "elementary-number-theory" tags, then we will get the posts which tag both “number-theory” and "elementary-number-theory" :


questions tagged

(number-theory) (elementary-number-theory)

So the relationship between them is "and", I'd like to search the post which tag is "number-theory " or "elementary-number-theory", hence the relationship between them is "or", I wonder if one can do this ?

  • 9
    $\begingroup$ Currently the tags are just friends, but rumor has it that [number-theory] is going to change its Facebook to "It's complicated" and [elementary-number-theory] won't. $\endgroup$
    – Asaf Karagila Mod
    Jul 18, 2013 at 15:53
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    $\begingroup$ @Asaf Karagila You exactly answered my question in the title! $\endgroup$
    – lsr314
    Jul 18, 2013 at 15:59
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    $\begingroup$ meta.SO: Search (tag1) OR (tag2) $\endgroup$ Jul 20, 2013 at 14:50
  • $\begingroup$ You can also use filters to view questions from some set of tags. (But MathJax is not rendered in the titles there.) $\endgroup$ Jul 20, 2013 at 14:52
  • $\begingroup$ See also Filtering by tag. $\endgroup$ Jan 4, 2015 at 10:25

1 Answer 1


I just tried putting [number-theory] or [elementary-number-theory] in the search box, and it seems to work. I get 8,011 questions tagged (number-theory) or (elementary-number-theory).

  • $\begingroup$ that's ok,thank you! $\endgroup$
    – lsr314
    Jul 18, 2013 at 15:46
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    $\begingroup$ What if I want to search for [number-theory] xor [elementary-number-theory]? $\endgroup$ Jul 21, 2013 at 0:27
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    $\begingroup$ It is possible to exclude a tag from your search by preceding it with -. For example, you can search for [number-theory] -[elementary-number-theory] or the other way around. The xor syntax is not supported, possibly because there is no realistic use case for it. $\endgroup$
    – 40 votes
    Jul 21, 2013 at 0:38

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