Homologier

Homologier is the plural form of the noun homologi in several Scandinavian languages, notably Swedish, Danish, and Norwegian, and is used to refer to the concept of homology. In English, the equivalent term is homology (plural homologies). The word is used in both biology and mathematics, where it denotes different but related ideas about structural similarity and invariants.

In biology, homologier describe similarity between parts or genes that arises from shared ancestry. Structural homologier include features such as the forelimbs of humans, whales, and bats that have the same basic arrangement despite different functions. Genetic homologier refer to DNA sequences or genes that are descended from a common ancestor, including orthologs (across species) and paralogs (within a species). Distinguishing homologier from analogous traits is a core task in comparative anatomy and evolutionary biology, as analogies result from convergent evolution rather than shared origin. Identifying homologier often relies on comparative anatomy, phylogenetic analysis, and sequence alignment.

In mathematics, homologier describe a family of invariants that classify topological or algebraic structures. Homology assigns algebraic objects, such as groups, to spaces, capturing information about holes of various dimensions. This yields homology groups and, in applications, Betti numbers, which summarize the structure’s features. Common versions include singular homology and simplicial homology, used across algebraic topology, geometry, and data analysis.

Etymology: from Greek homologia, meaning agreement or correspondence. See also homology, orthology, paralogy, and topology.