homologous
UK[hɒˈmɒləɡəs]US[hoʊˈmɑːləɡəs]
adj
Having the same relation, relative position, or structure, typically as a result of shared evolutionary origin.
adj
(in biology) Similar in position, structure, and evolutionary origin but not necessarily in function.
adj
(in chemistry) Describing a series of compounds with the same functional group but differing by a constant structural unit.
Morpheme Breakdown
homo
log
ous
homo
same
log
relation, word
ous
adjective suffix
Etymology
The word "homologous" is a scientific term constructed from classical components to express a precise relational concept. It combines the Greek homos (same) with logos, which in this context extends from its core meaning of "word" or "reason" to denote a "relation" or "proportion". The Latin-derived adjectival suffix -ous was later appended. Thus, the literal construction "having the same relation" perfectly captures its modern use across biology, chemistry, and general science to describe structural or positional correspondence stemming from a common origin, distinct from mere superficial similarity (analogy).
Analysis
Structure: homo (same) + log (relation, word) + ous (adjective suffix)
homo: From Greek homos, meaning "same". It functions as a prefix indicating sameness or similarity.
log: From Greek logos, meaning "word, speech, reason, proportion, relation". In this compound, it conveys the sense of "relation" or "proportion".
ous: A suffix of Latin origin (-osus) via Old French, used to form adjectives meaning "full of" or "having the quality of".
Examples
The wing of a bat and the arm of a human are homologous structures.
These two chromosomes are homologous and pair during meiosis.
Methane, ethane, and propane are the first three members of the homologous series of alkanes.