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