A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
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sequencesandseries× 317  harmonicanalysis× 316  sheaftheory× 315 
abelianvarieties× 314
projective algebraic varieties endowed with an Abelian group structure. Over the complex numbers, they can be described as quotients of a vector space by a lattice of full rank. …

computerscience× 310
For question borderline with, or having application to, computer science. Consider also posting http://cs.stackexchange.com/ or http://cstheory.stackexchange.com/ instead of here, if appropriate.

discretegeometry× 306
Finite or discrete collections of geometric objects. Packings, tilings, polyhedra, polytopes, intersection, arrangements, rigidity.

vectorbundles× 303 
openproblem× 302
equivalent to a known open problem, then the openproblem tag is added. After that, the question essentially becomes, "What is known about this problem? What are some…

examples× 300 
forcing× 294
a method first used to prove the continuum hypothesis is independent of the classical axioms of set theory

convexpolytopes× 291
the convex hulls of a finite set of points in Euclidean spaces. They have rich combinatorial, arithmetic, and metrical theory, and are related to toric varieties and to linear pr…

inequalities× 286 
simplicialstuff× 286 
ergodictheory× 285
Dynamical systems on measure spaces, invariant measures, ergodic averages, mixing properties.

lattices× 279  hyperbolicgeometry× 278 
sp.spectraltheory× 273
Schrodinger operators, operators on manifolds, general differential operators, numerical studies, integral operators, discrete models, resonances, nonselfadjoint operators, random operators/matrices…

galoistheory× 273  groupcohomology× 253  terminology× 250 
convexity× 249  integration× 247 
specialfunctions× 246
Many special functions appear as solutions of differential equations or integrals of elementary functions. Most special functions have relationships with representation theory of Lie groups.

riemannsurfaces× 245 
deformationtheory× 233 
it.informationtheory× 231
Covers theoretical and experimental aspects of information theory and coding.

convexgeometry× 230  diophantineequations× 229 
etalecohomology× 225  modelcategories× 224 
bigpicture× 221
Questions designed to get an overview of a specific subject or body of results or to understand the relations among similar definitions, techniques or concepts appearing in different subfields of mat…

automorphicforms× 218 
galoisrepresentations× 218  axiomofchoice× 214  stacks× 214  stochasticcalculus× 210 