16S10 Rings determined by universal properties (free algebras, coproducts, adjunction of inverses, etc.)
16S15 Finite generation, finite presentability, normal forms (diamond lemma, term-rewriting)
16S20 Centralizing and normalizing extensions
16S30 Universal enveloping algebras of Lie algebras [See mainly 17B35]
16S32 Rings of differential operators [See also 13N10, 32C38]
16S34 Group rings [See also 20C05, 20C07], Laurent polynomial rings
16S35 Twisted and skew group rings, crossed products
16S36 Ordinary and skew polynomial rings and semigroup rings [See also 20M25]
16S37 Quadratic and Koszul algebras
16S38 Rings arising from non-commutative algebraic geometry
16S40 Smash products of general Hopf actions [See also 16W30]
16S50 Endomorphism rings; matrix rings [See also 15-XX]
16S60 Rings of functions, subdirect products, sheaves of rings
16S70 Extensions of rings by ideals
16S80 Deformations of rings [See also 13D10, 14D15]
16S90 Maximal ring of quotients, torsion theories, radicals on module categories [See also 13D30, 18E40] {For radicals of rings, see 16Nxx}
16S99 None of the above, but in this section