homologue
UK[ˈhɒməlɒɡ]US[ˈhoʊməlɔːɡ]
n
A thing that has the same relative position, structure, or evolutionary origin as another thing, but not necessarily the same function.
n
(Chemistry) One of a series of compounds in which successive members differ by a constant molecular unit.
Morpheme Breakdown
homo
logue
homo
same
logue
speech, relation
Etymology
The word 'homologue' is built from two Greek elements. The first, homo-, meaning "same," is a fundamental root of comparison. The second, -logue, derives from logos, a term with a vast semantic range encompassing word, reason, principle, and relation. In scientific terminology, -logue came to signify something connected by a proportional or analogous relationship. Thus, the literal combination "same relation" perfectly captures the modern abstract meaning: an element in one system that corresponds to another due to shared origin, position, or structural plan, even if their superficial functions differ. This logic allows the term to be applied consistently across biology, chemistry, and anatomy.
Analysis
Structure: homo (same) + logue (speech, relation)
homo: From Greek homos, meaning "same, one and the same, common." It functions as a combining form indicating sameness or similarity.
logue: From Greek logos, meaning "word, speech, discourse, reason." In this context, it functions as a suffix denoting something related by proportion or analogy.
Examples
The human arm is considered a homologue of the whale's flipper.
In this chemical series, each homologue has an additional methylene group.
The gene found in mice has a direct homologue in the human genome.