18Gxx Homological algebra [See also 13Dxx, 16Exx, 20Jxx, 55Nxx, 55Uxx, 57Txx]
 18G05 Projectives and injectives [See also 13C10, 13C11, 16D40, 16D50]
 18G10 Resolutions; derived functors [See also 13D02, 16E05, 18E25]
 18G15 Ext and Tor, generalizations, Künneth formula [See also 55U25]
 18G20 Homological dimension [See also 13D05, 16E10]
 18G25 Relative homological algebra, projective classes
 18G30 Simplicial sets, simplicial objects (in a category) [See also 55U10]
 18G35 Chain complexes [See also 18E30, 55U15]
 18G40 Spectral sequences, hypercohomology [See also 55Txx]
 18G50 Nonabelian homological algebra

18G55 Homotopical algebra
(1)
 18G60 Other (co)homology theories [See also 19D55, 46L80, 58J20, 58J22]
 18G99 None of the above, but in this section