What does corollary mean?
A corollary is a proposition or fact that follows so directly from something already established that it requires little or no separate proof. The term originates in formal logic and mathematics, where a corollary appears alongside a theorem as its ready-made extension, but in everyday language the word has broadened to describe any natural consequence of an action or circumstance — for example, the corollary of a booming economy might be rising rents. Because it implies a tight, almost inevitable link between cause and effect, corollary carries an intellectual, somewhat formal connotation; it is at home in essays, legal argument, and scholarly prose rather than light conversation. Writers often strengthen it with adjectives such as "necessary," "logical," or "inevitable." Knowing this word allows you to express consequential reasoning precisely: to say something is a corollary is to claim it follows not accidentally but by clear logical necessity from what came before.
nounA proposition that follows directly and easily from something already proved; more broadly, a natural consequence or result that follows from an action, situation, or set of circumstances.
- A proposition that follows readily from another already established, especially in mathematics and logic.
- A natural consequence or by-product that follows from a condition, event, or course of action.
"The rise in remote work brought a corollary decline in demand for city-centre office space."
"In Euclidean geometry, the theorem's corollary was stated immediately beneath it as an obvious extension."
"A corollary of the company's rapid expansion was a noticeable dilution of its once-tight company culture."
Standard pluralization; note the -ies ending follows the regular rule for words ending in consonant + y.
"The paper listed two corollaries of the main theorem."
"Corollary" comes from the Latin word for a garland of flowers — a small gift added to a payment — which is why it still carries the sense of a bonus that arrives automatically.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of corollary
"Corollary" derives from the Latin "corollarium", originally meaning money paid for a garland or a small gratuity added on to a payment, itself formed from "corolla", a little crown or garland of flowers. In medieval Latin scholastic usage the term came to denote a proposition appended to a proven statement as an immediate consequence, and English adopted this learned mathematical sense in the late 16th or early 17th century. Its botanical cognates include "corolla", the collective name for a flower's petals, sharing the same Latin root.
How corollary is actually used
Formal in register: common in academic writing, philosophy, mathematics, law, and serious journalism, but rare in casual conversation. Often used with modifiers like "necessary," "logical," or "inevitable." In mathematics it retains the precise technical sense of a theorem requiring little additional proof.
Easily confused with corollary
Corollary is a noun meaning a consequence that follows from a statement or action; corelation (more commonly written correlation) refers to a statistical relationship between variables.
This is simply the plural form of corollary itself — multiple propositions following from one proof — not a separate word.