13-XX Commutative rings and algebras
13-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
13-01 Instructional exposition (textbooks, tutorial papers, etc.)
13-02 Research exposition (monographs, survey articles)
13-03 Historical {!must also be assigned at least one classification number from section 01}
13-04 Explicit machine computation and programs (not the theory of computation or programming)
13-06 Proceedings, conferences, collections, etc.
13Axx General commutative ring theory
13A02 Graded rings [See also 16W50]
13A05 Divisibility
13A10 Radical theory
13A15 Ideals; multiplicative ideal theory
13A18 Valuations and their generalizations [See also 12J20]
13A30 Associated graded rings of ideals (Rees ring, form ring), analytic spread and related topics
13A35 Characteristic p methods (Frobenius endomorphism) and reduction to characteristic p; tight closure [See also 13B22]
13A50 Actions of groups on commutative rings; invariant theory [See also 14L25]
13A99 None of the above, but in this section
13Bxx Ring extensions and related topics
13B02 Extension theory
13B05 Galois theory (commutative rings)
13B10 Morphisms
13B21 Integral dependence
13B22 Integral closure of rings and ideals; integrally closed rings, related rings (Japanese, etc.)
13B24 Going up; going down; going between
13B25 Polynomials over commutative rings [See also 11C08, 13F20, 13M10]
13B30 Quotients and localization
13B35 Completion [See also 13J10]
13B40 \'Etale and flat extensions; Henselization; Artin approximation [See also 13J15, 14B12, 14B25]
13B99 None of the above, but in this section
13Cxx Theory of modules and ideals
13C05 Structure, classification theorems
13C10 Projective and free modules and ideals [See also 19A13]
13C11 Injective and flat modules and ideals
13C12 Torsion modules and ideals
13C13 Other special types
13C14 Cohen - Macaulay modules [See also 13H10]
13C15 Dimension theory, depth, related rings (catenary, etc.)
13C20 Class groups [See also 11R29]
13C40 Linkage, complete intersections and determinantal ideals [See also 14M12]
13C99 None of the above, but in this section
13Dxx Homological methods {For noncommutative rings, see 16Exx; for general categories, see 18Gxx}
13D02 Syzygies and resolutions
13D03 (Co)homology of commutative rings and algebras (e.g., Hochschild, Andr\'e - Quillen, cyclic, dihedral, etc.)
13D05 Homological dimension
13D07 Homological functors on modules (Tor, Ext, etc.)
13D10 Deformations and infinitesimal methods [See also 14B10, 14B12, 14D15, 32Gxx]
13D15 Grothendieck groups, K-theory [See also 14C35, 18F30, 19Axx, 19D50]
13D22 Homological conjectures (intersection theorems)
13D25 Complexes
13D30 Torsion theory [See also 13C12, 18E40]
13D40 Hilbert - Samuel and Hilbert - Kunz functions; Poincar\'e series
13D45 Local cohomology [See also 14B15]
13D99 None of the above, but in this section
13Exx Chain conditions, finiteness conditions
13E05 Noetherian rings and modules
13E10 Artinian rings and modules, finite-dimensional algebras
13E15 Rings and modules of finite generation or presentation; number of generators
13E99 None of the above, but in this section
13Fxx Arithmetic rings and other special rings
13F05 Dedekind, Pr\"ufer and Krull rings and their generalizations
13F07 Euclidean rings and generalizations
13F10 Principal ideal rings
13F15 Factorial rings, unique factorization domains [See also 14M05]
13F20 Polynomial rings and ideals; rings of integer-valued polynomials [See also 11C08, 13B25]
13F25 Formal power series rings [See also 13J05]
13F30 Valuation rings [See also 13A18]
13F40 Excellent rings
13F45 Seminormal rings
13F50 Rings with straightening laws, Hodge algebras
13F55 Face and Stanley - Reisner rings; simplicial complexes [See also 55U10]
13F99 None of the above, but in this section
13G05 Integral domains
13Hxx Local rings and semilocal rings
13H05 Regular local rings
13H10 Special types (Cohen - Macaulay, Gorenstein, Buchsbaum, etc.) [See also 14M05]
13H15 Multiplicity theory and related topics [See also 14C17]
13H99 None of the above, but in this section
13Jxx Topological rings and modules [See also 16W60, 16W80]
13J05 Power series rings [See also 13F25]
13J07 Analytical algebras and rings [See also 32B05]
13J10 Complete rings, completion [See also 13B35]
13J15 Henselian rings [See also 13B40]
13J20 Global topological rings
13J25 Ordered rings [See also 06F25]
13J30 Real algebra [See also 12Dxx, 14Pxx]
13J99 None of the above, but in this section
13K05 Witt vectors and related rings
13L05 Applications of logic to commutative algebra [See also 03Cxx, 03Hxx]
13Mxx Finite commutative rings {For number-theoretic aspects, see 11Txx}
13M05 Structure
13M10 Polynomials
13M99 None of the above, but in this section
13Nxx Differential algebra [See also 12H05, 14F10]
13N05 Modules of differentials [See also 16S32]
13N10 Rings of differential operators and their modules [See also 16S32, 32C38]
13N15 Derivations
13N99 None of the above, but in this section
13Pxx Computational aspects of commutative algebra [See also 68W30]
13P05 Polynomials, factorization [See also 12Y05]
13P10 Polynomial ideals, Gr\"obner bases [See also 13F20]
13P99 None of the above, but in this section