Number & MeasureGreek → English
Homology
/həˈmɑlədʒi/noun
In mathematics, an algebraic structure that counts the holes in a space; in biology, sameness of structure inherited from a common ancestor.
The Greek roots
ὁμός
homós
same
λόγος
lógos
ratio, proportion, account
Literally: “same ratio”
The story of the word
λόγος means ratio as readily as it means word, and that is the sense doing the work here. Poincaré built the mathematical version in his Analysis Situs of 1895, where two cycles are homologous when their difference is the boundary of something. Richard Owen had already taken the word for anatomy in 1843, setting homology, a bat's wing and a human hand, against analogy, a bat's wing and a bee's.
- How it travelled
- Ancient Greek → scientific coinage → English
The same roots elsewhere
Other languages reached for exactly the same Greek pieces.
Same family
cohomologyhomologousanalogyhomogeneous
In a sentence
The first homology group of a torus has rank two, one for each independent loop.