rationale

Merriam-Webster's Word of the Day for September 18, 2025 is: rationale \rash-uh-NAL\ noun Rationale refers to an explanation or reason for something said or done. It is often used with for, behind, or of. // City council members who oppose the zoning change should be ready to explain their rationale for voting against it. // She’s explained the rationale behind her early retirement. [See the entry >](https://www.merriam-webster.com/dictionary/rationale) Examples: “There is a rationale for commercializing [seagrass](https://www.merriam-webster.com/dictionary/seagrass) production, but ecologically sustainable production needs to be at the heart of that business model, and the numbers for doing that simply don’t add up at the moment.” — Richard Lilley, quoted in Smithsonian Magazine, 7 Oct. 2024 Did you know? If someone asserts that the word rationale refers to a [ration](https://www.merriam-webster.com/dictionary/ration) of [ale](https://www.merriam-webster.com/dictionary/ale), they are wrong, but that doesn’t mean they don’t have an actual rationale (a reason, explanation, or basis) for such a claim. “Rationale looks like the words ration and ale jammed together,” they could offer, and while that is true you’d be justified in responding: “Appearances can be deceiving.” Rationale is a direct borrowing of the Latin word rationale, with which it shares the meaning “an explanation of controlling principles of opinion, belief, practice, or phenomena.” The Latin rationale comes from a form of the adjective rationalis (“[rational](https://www.merriam-webster.com/dictionary/rational)”), which traces back to the noun ratio, meaning “reason.” While the Latin ratio is also the forebear of the English noun [ration](https://www.merriam-webster.com/dictionary/ration), referring to a share of something, rationale has nothing to do with a tankard (or stein, or even a [pony](https://www.merriam-webster.com/dictionary/pony)) of beer.