20G15 Linear algebraic groups over arbitrary fields

20G20 Linear algebraic groups over the reals, the complexes, the quaternions

20G25 Linear algebraic groups over local fields and their integers

20G30 Linear algebraic groups over global fields and their integers

20G35 Linear algebraic groups over adèles and other rings and schemes

20G40 Linear algebraic groups over finite fields

20G42 Quantum groups (quantized function algebras) and their representations [See also <a href="#code:16T20">16T20</a>, <a href="#code:17B37">17B37</a>, <a href="#code:81R50">81R50</a>]

20G99 None of the above, but in this section

20Hxx Other groups of matrices [See also <a href="#code:15A30">15A30</a>]

20H05 Unimodular groups, congruence subgroups [See also <a href="#code:11F06">11F06</a>, <a href="#code:19B37">19B37</a>, <a href="#code:22E40">22E40</a>, <a href="#code:51F20">51F20</a>]

20H10 Fuchsian groups and their generalizations [See also <a href="#code:11F06">11F06</a>, <a href="#code:22E40">22E40</a>, <a href="#code:30F35">30F35</a>, <a href="#code:32Nxx">32Nxx</a>]

20H15 Other geometric groups, including crystallographic groups [See also <a href="#code:51-XX">51-XX</a>, especially <a href="#code:51F15">51F15</a>, and <a href="#code:82D25">82D25</a>]

20H30 Other matrix groups over finite fields

20H99 None of the above, but in this section

20Jxx Connections with homological algebra and category theory

20J05 Homological methods in group theory

20J99 None of the above, but in this section

20K01 Finite abelian groups [For sumsets, see <a href="#code:11B13">11B13</a> and <a href="#code:11P70">11P70</a>]

20K10 Torsion groups, primary groups and generalized primary groups

20K20 Torsion-free groups, infinite rank

20K25 Direct sums, direct products, etc.

20K30 Automorphisms, homomorphisms, endomorphisms, etc.

20K40 Homological and categorical methods

20K45 Topological methods [See also <a href="#code:22A05">22A05</a>, <a href="#code:22B05">22B05</a>]

20K99 None of the above, but in this section

20Lxx Groupoids (i.e. small categories in which all morphisms are isomorphisms) {For sets with a single binary operation, see <a href="#code:20N02">20N02</a>; for topological groupoids, see <a href="#code:22A22">22A22</a>, <a href="#code:58H05">58H05</a>}