The relationship of being homologous; a homologous relationship. • specifically, such relationship in the context of the geometry of perspective. • An automorphism of the projective plane (representing a perspective projection) that leaves all the points of some straight line (the homology axis) fixed and maps all the lines through some single point (the homology centre) onto themselves. • A general way of associating a sequence of algebraic objects, such as abelian groups or modules, to a sequence of topological spaces; also used attributively: see Usage notes below. • Given a chain complex {Gₙ} and its associated set of homomorphisms {Hₙ}, the rule which explains how each Hₙ maps Gₙ into the kernel of Gₙ₊₁. • The relationship, between elements, of being in the same group of the periodic table. • The relationship, between organic compounds, of being in the same homologous series. • The relationship, between characteristics or behaviours, of having a shared evolutionary or developmental origin; • The relationship, between characteristics or behaviours, of having a shared evolutionary or developmental origin; (evolutionary theory) specifically, a correspondence between structures in separate life forms having a common evolutionary origin, such as that between mammalian flippers and hands. • specifically, a correspondence between structures in separate life forms having a common evolutionary origin, such as that between mammalian flippers and hands. • The presence of the same series of bases in different but related genes. • The relationship, between temporally separated human beliefs, practices or artefacts, of possessing shared characteristics attributed to genetic or historical links to a common ancestor.