Analogues

An analogue, or analog in American spelling, is something that bears a similarity or correspondence to another thing in form, function, or relation. The term is widely used across disciplines to indicate a counterpart that can stand in for the other in analysis, modeling, or comparison. It is often used as an adjective or noun.

In chemistry and pharmacology, a structural analogue is a compound whose core skeleton is the same or closely related to another compound, but with one or more substituents altered. Analogues are used to explore structure–activity relationships, refine potency, selectivity, or pharmacokinetic properties, and to study mechanisms of action.

In biology, analogues denote traits or organs that are similar in function or appearance but do not share a common evolutionary origin, due to convergent evolution. For example, the wings of bats and birds are analogues rather than homologous. The term warrants careful use to distinguish from homologues, which arise by descent from a common ancestor.

In mathematics and linguistics, analogues refer to concepts or objects that play similar roles in different theories or languages. Analogical reasoning transfers knowledge from one domain to another, and researchers describe analogues of theorems, models, or grammatical structures to highlight parallel structures.

In technology, the word analogue also appears in the sense of continuous signals, devices, or processes that vary smoothly, as opposed to digital, discrete representations. An analogue signal can be processed, measured, or converted to a digital form for computation.