00-XX	G General
01-XX	G History and biography [See also the classification number -03 in the other sections]
03-XX	G Mathematical logic and foundations
05-XX	G Combinatorics {For finite fields, see 11Txx}
06-XX	G Order, lattices, ordered algebraic structures [See also 18B35]
08-XX	G General algebraic systems
11-XX	G Number theory
12-XX	G Field theory and polynomials
13-XX	G Commutative rings and algebras
14-XX	G Algebraic geometry
15-XX	G Linear and multilinear algebra; matrix theory
16-XX	G Associative rings and algebras {For the commutative case, see 13-XX}
17-XX	G Nonassociative rings and algebras
18-XX	G Category theory; abstract homological algebra {See 13Dxx for commutative rings, 16Exx for associative rings, 20Jxx for groups, 57Txx for topological groups and related structures; see also 55Nxx and 55Uxx for algebraic topology}
19-XX	G $K$-theory [See also 16E20, 18F25]
20-XX	G Group theory and generalizations
22-XX	G Topological groups, Lie groups {For transformation groups, see 54H15, 57Sxx, 58-XX. For abstract harmonic analysis, see 43-XX}
26-XX	G Real functions [See also 54C30]
28-XX	G Measure and integration {For analysis on manifolds, see 58-XX}
30-XX	G Functions of a complex variable {For analysis on manifolds, see 58-XX}
31-XX	G Potential theory {For probabilistic potential theory, see 60J45}
32-XX	G Several complex variables and analytic spaces {For infinite-dimensional holomorphy, see also 46G20, 58B12}
33-XX	G Special functions {! 33-XX deals with the properties of functions as functions} {For orthogonal functions, see also 42Cxx; for aspects of combinatorics, see 05Axx; for number-theoretic aspects, see 11-XX; for representation theory, see 22Exx}
34-XX	G Ordinary differential equations
35-XX	G Partial differential equations
37-XX	G Dynamical systems and ergodic theory [See also 26A18, 34Cxx, 34Dxx, 35Bxx, 46Lxx, 58Jxx, 70-XX]
39-XX	G Difference and functional equations
40-XX	G Sequences, series, summability
41-XX	G Approximations and expansions {For all approximation theory in the complex domain, see 30Exx, 30E05 and 30E10; for all trigonometric approximation and interpolation, see 42Axx, 42A10 and 42A15; for numerical approximation, see 65Dxx}
42-XX	G Fourier analysis
43-XX	G Abstract harmonic analysis {For other analysis on topological and Lie groups, see 22Exx}
44-XX	G Integral transforms, operational calculus {For fractional derivatives and integrals, see 26A33. For Fourier transforms, see 42A38, 42B10. For integral transforms in distribution spaces, see 46F12. For numerical methods, see 65R10}
45-XX	G Integral equations
46-XX	G Functional analysis {For manifolds modeled on topological linear spaces, see 57N20, 58Bxx}
47-XX	G Operator theory
49-XX	G Calculus of variations and optimal control; optimization [See also 34H05, 34K35, 65Kxx, 90Cxx, 93-XX]
51-XX	G Geometry {For algebraic geometry, see 14-XX}
52-XX	G Convex and discrete geometry
53-XX	G Differential geometry {For differential topology, see 57Rxx. For foundational questions of differentiable manifolds, see 58Axx}
54-XX	G General topology {For the topology of manifolds of all dimensions, see 57Nxx}
55-XX	G Algebraic topology
57-XX	G Manifolds and cell complexes {For complex manifolds, see 32Qxx}
58-XX	G Global analysis, analysis on manifolds [See also 32Cxx, 32Fxx, 46-XX, 47Hxx, 53Cxx] {For geometric integration theory, see 49Q15}
60-XX	G Probability theory and stochastic processes {For additional applications, see 11Kxx, 62-XX, 90-XX, 92-XX, 93-XX, 94-XX}
62-XX	G Statistics
65-XX	G Numerical analysis
68-XX	G Computer science {For papers involving machine computations and programs in a specific mathematical area, see section -04 in that area}
70-XX	G Mechanics of particles and systems {For relativistic mechanics, see 83A05 and 83C10; for statistical mechanics, see 82-XX}
74-XX	G Mechanics of deformable solids
76-XX	G Fluid mechanics {For general continuum mechanics, see 74Axx or other parts of 74-XX}
78-XX	G Optics, electromagnetic theory {For quantum optics, see 81V80}
80-XX	G Classical thermodynamics, heat transfer {For thermodynamics of solids, see 74A15}
81-XX	G Quantum theory
82-XX	G Statistical mechanics, structure of matter
83-XX	G Relativity and gravitational theory
85-XX	G Astronomy and astrophysics {For celestial mechanics, see 70F15}
86-XX	G Geophysics [See also 76U05, 76V05]
90-XX	G Operations research, mathematical programming
91-XX	G Game theory, economic, social and behavioral sciences
92-XX	G Biology and other natural sciences
93-XX	G Systems theory; control {For optimal control, see 49-XX}
94-XX	G Information and communication, circuits
97-XX	G Mathematics education