It seems like these are nearly identical in nature. The tag for complex integration was created three months ago and the contour-integration tag has been around for over two years. I feel like the complex-integration tag should be a synonym for contour-integration.

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    $\begingroup$ Hmmm. I am inclined to agree, as virtually all instances of contour-integration indicate the complex plane. But is this necessarily the case? How about real line integrals over curves in $\mathbb{R}^2$? $\endgroup$
    – Ron Gordon
    Dec 22 '14 at 19:56
  • $\begingroup$ There's a separate line-integrals tag floating around somewhere which would take care of that, I think. Line integral problems don't show up quite as much, so I think it's okay to distinguish contour integration from line integration. Also the wiki for contour-integration specifically has complex plane integration in mind for that matter. $\endgroup$ Dec 22 '14 at 19:58
  • $\begingroup$ when starting complex analysis, sometimes there are problems asking one to integrate complex functions that are not complex-differentiable over curves in $\mathbb{C}$. These are the only reason I might see for the complex-integration tag. $\endgroup$
    – robjohn Mod
    Dec 22 '14 at 20:01
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    $\begingroup$ @robjohn: I think those cases would still fall under the umbrella of contour integration; the contour integral is defined without regard to differentiability, e.g. via Riemann-Stieltjes integration. Even when concerned primarily with holomorphic functions, one uses contour integrals for functions not a priori known to be holomorphic, e.g. in applying Morera's theorem. $\endgroup$ Dec 22 '14 at 20:15
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    $\begingroup$ One could integrate over a subset of the plane that is not a contour. However, the description of complex integration tag suggests it is to be used synonymously with contour integration. So I think the tags should be synonyms. $\endgroup$
    – user147263
    Dec 22 '14 at 20:29
  • $\begingroup$ @Behaviour we could easily integrate a complex valued function without using a contour. For instance, take this post, I would call this complex integration but it wouldn't fit in with contour integration. $\endgroup$
    – dustin
    Dec 22 '14 at 21:05
  • $\begingroup$ @dustin Why would not it fit? There's a contour of integration right there, the boundary of the rectangle. $\endgroup$
    – user147263
    Dec 22 '14 at 21:10
  • $\begingroup$ @Behaviour You are correct. I was thinking of something else. I was thinking of it as solely applying to residues. $\endgroup$
    – dustin
    Dec 22 '14 at 21:12
  • $\begingroup$ Wait, do people actually distinguish between contour, line, and path integrals? To me, they are synonymous and make sense for any nice manifold, not just the complex plane. $\endgroup$ Dec 24 '14 at 19:24
  • $\begingroup$ @SpamIAm I think they only distinguish contour integrals as they show up repeatedly in complex analysis although it's just a realization of a line integral. Just to distinguish the context easily. $\endgroup$ Dec 24 '14 at 20:39

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