homology

noun

ho·​mol·​o·​gy hō-ˈmä-lə-jē 

hə-

plural homologies

1

: a similarity often attributable to common origin

… the anthropologist is in the curious position of dealing with … striking homologies not necessarily due to historical contact …

—Edward Sapir

2

a

evolutionary biology : correspondence or similarity in form or function between parts (such as the wing of a bat and the human arm) of different species resulting from modification of a trait possessed by a common ancestor : similarity of traits reflecting common descent and ancestry compare analogy, homoplasy

b

anatomy : correspondence in structure between a series of parts (such 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 (such 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.

Examples of homology in a Sentence

Recent Examples on the Web

Which part of the complex manifold’s homology can be obtained by looking at these topological invariants? —Quanta Magazine, 13 Mar. 2024

There is an object, called a homology, which gives you a lot of topological information about the manifold. —Quanta Magazine, 13 Mar. 2024

By the end of that decade those methods had blossomed into an entire area of study, Heegaard Floer homology, and within that area there are now a number of different approaches to distinguishing manifolds. —Kevin Hartnett, Quanta Magazine, 22 Feb. 2024

Mathematician Jose Perea of Northeastern University and a team of computational biologists used persistent homology to find periodic biological processes—those that repeat at regular intervals. —Kelsey Houston-Edwards, Scientific American, 21 Sep. 2022

These became known as generalized homology theories. —Quanta Magazine, 9 Dec. 2021

Solidarity between oppressed peoples across the globe isn't about a perfect homology. —Cherrell Brown, refinery29.com, 21 June 2021

To find these implicit pictures, mathematicians use a technique known as persistent homology. —Kelsey Houston-Edwards, Scientific American, 21 Sep. 2022

After using some standard techniques to simplify the data, the team computed the persistent homology of the system by connecting the data points at different scales and examining the resulting simplicial complexes. —Kelsey Houston-Edwards, Scientific American, 21 Sep. 2022

Word History

First Known Use

circa 1656, in the meaning defined at sense 1

Kids Definition

homology

noun

ho·​mol·​o·​gy hō-ˈmäl-ə-jē 

hə-

plural homologies

: a likeness often due to common origin: as

a

: structural likeness between corresponding parts (as the wing of a bat and the arm of a human being) of different plants or animals due to evolution from a common ancestor in the distant past

b

: structural likeness between a series of parts (as vertebrae) in the same individual

Medical Definition

homology

noun

ho·​mol·​o·​gy hō-ˈmäl-ə-jē, hə- 

plural homologies

1

a

: 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, homomorphy

b

: correspondence in structure between different parts of the same individual

2

a

: 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 CH₂

b

: the relation existing among elements in the same group of the periodic table

c

: similarity of nucleotide or amino acid sequence (as in nucleic acids or proteins)