homology

noun

1. 1.A homologous relationship.
2. 2.A theory associating a system of groups to each topological space.
3. 3.A certain system of groups associated to a chain complex.
4. 4.The relationship between the elements in the same group of the periodic table, or between organic compounds in a homologous series.
5. 5.A correspondence of structures in two life forms with a common evolutionary origin, such as flippers and hands.