/əˈnæl.ə.ɡəs/
[adjective] Similar to something else in some important way, so that a comparison between the two helps you understand one of them better. For example, the human heart is analogous to a pump.
This word carries ancient mathematical DNA — the Greeks used it purely for numbers before it grew to describe any similarity in the universe.
The story of 'analogous' begins in ancient Greece, where mathematicians needed precise language to describe proportional relationships between numbers. The Greek word 'analogos' was built from two parts: 'ana', meaning 'according to' or 'up to', and 'logos', meaning 'ratio', 'word', or 'reason'. So 'analogos' originally meant something very specific — 'according to a ratio' — and it lived strictly in the world of mathematics and geometry, used to describe numbers that bore the same proportion to each other, the way 4 is to 8 as 6 is to 12.
From this technical mathematical root, the Greek word began to stretch. Greek philosophers, particularly Aristotle, started using 'analogia' — the noun form — to describe not just numerical ratios but any kind of structural similarity between things. When Aristotle wrote that the fin of a fish is analogous to the wing of a bird, he was making a bold leap: he was saying that the relationship of fin to fish mirrors the relationship of wing to bird, even though fins and wings look nothing alike. This was analogy as intellectual tool, a way of mapping one domain of knowledge onto another.
The word passed from ancient Greek into Latin as 'analogus', used by Roman writers and scholars who preserved the broader philosophical sense. From Latin, it moved into learned European writing during the Renaissance, when scholars across Europe were rediscovering classical texts and importing their vocabulary wholesale into English, French, and other modern languages. The English word 'analogous' appears in written records from the mid-17th century, arriving through the Latin 'analogus', which itself came directly from the Greek 'analogos'.
What is remarkable about 'analogous' is how completely it shed its original mathematical skin. Today, almost nobody uses it to mean 'in the same numerical ratio'. Instead, it carries the broader Aristotelian sense — describing any two things that play a similar role or share a comparable structure, even in completely different contexts. Scientists use it to describe organs that perform the same function but evolved independently; lawyers use it to argue that one legal case resembles another; teachers use it to build bridges between unfamiliar ideas and ones students already understand.
The family of words that grew from the same Greek roots is rich and widely used. The Greek 'logos' gave English an enormous number of words via Latin: 'logic', 'dialogue' (Greek 'dia' + 'logos'), and the suffix '-logy' seen in 'biology', 'geology', and hundreds more. The prefix 'ana-' contributed to words like 'analysis' (Greek 'analyein', to unloose → Latin 'analysis' → English 'analysis') and 'anatomy' (Greek 'anatome' → Latin 'anatomia' → English 'anatomy'). The noun 'analogy' (Greek 'analogia' → Latin 'analogia' → English 'analogy') and the verb 'analogise' sit right beside 'analogous' in the same word family, all carrying that ancient mathematical sense of proportion that has quietly powered some of history's greatest thinking.