analogous

Analogous is an adjective used to describe a similarity between two things that arises from functional or role-based resemblance rather than from a shared origin. The term is often employed to indicate that two processes, structures, or concepts are comparable in a particular respect, even if they are not otherwise closely related. The word derives from Latin analogus, from Greek análogos meaning “proportionate” or “according to a ratio.”

In biology, an analogous structure is one that serves a similar function in different species but evolved independently, so it does not reflect a shared ancestry. A classic example is the wings of insects and birds, which both enable flight but have different evolutionary origins. By contrast, homologous structures arise from a common ancestor and may perform different functions.

Beyond biology, analogous is used to describe formal or conceptual similarity in science, mathematics, and everyday language. For instance, researchers may say two physical systems are analogous if their governing equations have the same form; electrical circuits can be described as being analogous to mechanical spring-damping systems. In color theory, analogous colors are colors that are next to each other on the color wheel, sharing a common hue. In rhetoric or everyday speech, analogy is a method of reasoning that draws on an analogous comparison to illuminate a concept.