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Atlas.AlgebraicTopologyI.code.DirectLimitHomology

Homology commutes with filtered colimits. In the abelian category AddCommGrpCat, the degree-n homology functor on chain complexes preserves filtered colimits. This is the categorical content underlying Corollary 23.13 (singular homology commutes with direct limits of spaces) and Lemma 23 (homology of a direct limit of chain complexes is the direct limit of the homologies).