Definition of: homology

(hō·mol′ə·jē) noun
1. The state or quality of being homologous; correspondence in structure and properties.
2. Biol. The correspondence of a part or organ of one animal with a similar part or organ of another, determined by agreement in derivation and development from a like primitive origin, as the foreleg of a quadruped, the wing of a bird, and the pectoral fin of a fish: distinguished from analogy and contrasted with heterology.
3. Chem. A similarity in compounds having the same fundamental structure but differing in constituents by a regular succession of changes, as the alcohols.
4. Bacteriol. A relationship between a bacterium and the serum obtained from it. [<HOMO- + -LOGY]