What does homologous mean?
Homologous describes things that correspond because they share an origin or an underlying structural plan. Its best-known use is in biology and anatomy: a human arm, a whale flipper, and a bat wing are homologous structures because their bones are arranged according to the same basic plan, even though the limbs serve different functions. Homology therefore often provides evidence of common ancestry. In chemistry, a homologous series consists of related compounds that differ incrementally, commonly by a methylene group, while retaining the same functional group. The word is formal and technical, but it also has a broader use for closely corresponding elements in a system. Its companion noun, homology, names the correspondence itself. The distinction from analogous is important: homologous parts share an origin or structural pattern, whereas analogous parts resemble one another in function without necessarily having the same evolutionary origin.
adjectiveHaving the same origin, structure, position, or corresponding relationships, especially when comparing organisms or parts of organisms. In chemistry, belonging to a series whose members share the same functional group and differ by a consistent unit, usually a methylene group.
- Corresponding in structure, position, or evolutionary origin, especially among organisms or anatomical structures.
- Belonging to a homologous series in chemistry, with members differing incrementally in composition and sharing a common functional group.
- Corresponding or similar in a broader scientific or technical context.
"The forelimb of a human and the wing of a bird are homologous structures because they share the same basic bone arrangement inherited from a common ancestor."
"The researcher compared homologous genes in several species to identify changes associated with the disease."
"Members of the homologous alkane series each differ from the preceding compound by a methylene group."
Homologous is the word biologists use when two structures tell the story of shared ancestry.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does homologous come from?
Homologous comes through Latin from Greek homologos, formed from homos, meaning “same,” and -logos, meaning “relation” or “kind.” The word was adopted in scientific language for structures or corresponding entities that are alike in origin or arrangement. It belongs to a wider family of English words built on the same Greek root for sameness, including homogeneous and homonym.
Related word forms
How homologous is actually used
This is a formal scientific term, most common in biology, anatomy, paleontology, and chemistry. It is sometimes used more broadly for things that correspond closely, but that broader use can obscure the specific evolutionary or structural relationship.
Easily confused with homologous
Homologous parts share an origin or underlying structural plan, whereas analogous parts perform similar functions without necessarily sharing that origin.