Definition of homology
1 : a similarity often attributable to common origin
2 a : likeness in structure between parts of different organisms (as the wing of a bat and the human arm) due to evolutionary differentiation from a corresponding part in a common ancestor — compare analogy b : correspondence in structure between a series of parts (as vertebrae) in the same individual
3 : similarity of nucleotide or amino acid sequence (as in nucleic acids or proteins)
4 : a branch of the theory of topology concerned with partitioning space into geometric components (as points, lines, and triangles) and with the study of the number and interrelationships of these components especially by the use of group theory —called also homology theory — compare cohomology
Did You Know?
The similarity of a structure or function of parts of different origins based on their descent from a common evolutionary ancestor is homology. Analogy, by contrast, is a functional similarity of structure that is based on mere similarity of use. For example, the forelimbs of humans, bats, and deer are homologous; the form of construction and the number of bones in each are almost identical and represent adaptive modifications of the forelimb structure of their shared ancestor. The wings of birds and insects, on the other hand, are merely analogous; both are used for flight, but they do not share a common ancestral origin.
First Known Use of homology
Medical Definition of homology
1a: likeness in structure between parts of different organisms due to evolutionary differentiation from the same or a corresponding part of a remote ancestor—compare analogy, homomorphyb: correspondence in structure between different parts of the same individual
2a: the relation existing between chemical compounds in a series whose successive members have in composition a regular difference especially of one carbon and two hydrogen atoms CH2b: the relation existing among elements in the same group of the periodic tablec: similarity of nucleotide or amino acid sequence (as in nucleic acids or proteins)
Seen and Heard
What made you want to look up homology? Please tell us where you read or heard it (including the quote, if possible).