Merriam-Webster's Word of the Day for September 20, 2025 is:

enmity • \EN-muh-tee\  • noun

Enmity is a formal word that refers to a very deep unfriendly feeling, such as hatred or ill will, that is often felt mutually.

// Having to collaborate on the project only increased the bitter enmity between the two coworkers, who had never gotten along.

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Examples:

"Paul Monreal is a fourth-great-grandchild of Catherine and Patrick O'Leary, who endured the enmity of Chicagoans after they were wrongfully accused of starting the Great Chicago Fire, which legend said was started by a jittery dairy cow named Daisy." — William Lee, The Chicago Tribune, 5 July 2025

Did you know?

The resemblance between enmity and enemy is no coincidence: both words come from the Anglo-French word enemi, which literally translates to "enemy." And when you feel enmity for a particular person—that is, deep-seated dislike or ill will—"enemy" may very well be an apt descriptor for them. While it is possible to feel enmity for someone who does not share or return one’s animosity, enmity is typically used for mutual hatred or antagonism between people (or groups, factions, etc.), as when Edgar Allan Poe wrote of the families of Berlifitzing and Metzengerstein in his first published short story: "Never before were two houses so illustrious, mutually embittered by hostility so deadly. The origin of this enmity seems to be found in the words of an ancient prophecy—'A lofty name shall have a fearful fall ...'"

Merriam-Webster's Word of the Day for September 19, 2025 is:

succumb • \suh-KUM\  • verb

Succumbing is about yielding to something: someone who succumbs to a pressure or emotion stops trying to resist that pressure or emotion, and someone who succumbs to an injury or disease dies because of that injury or disease. The word is often followed by to.

// The program aims to help kids develop the strength of character required to avoid succumbing to peer pressure.

// Many patients diagnosed with the disease live healthy lives for years before succumbing to it.

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Examples:

“Occasionally, Dope Girls does succumb to style over substance, as if it doesn’t quite have the confidence to let its big, bold narrative unfold without any bells and whistles.” — Jon O’Brien, The Daily Beast, 8 Aug. 2025

Did you know?

Picture yourself serenely succumbing to sleep. Chances are that in the mental image you’ve just formed, you are in a recumbent position—that is, lying down. The position is baked into the etymology: both succumb and recumbent trace back to cumbere, a Latin verb meaning “to lie down.” While recumbency is typically literal, succumbing is about figuratively lying down before something—yielding to it, ceasing to resist it. The word is most often used with regard to faults and foibles and demise—people succumb to temptation, plants succumb to blight—but the word can be applied in happier contexts too, as when one succumbs to sleep in a quiet spot on a sunny afternoon.

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.

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Examples:

“There is a rationale for commercializing 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 of 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”), which traces back to the noun ratio, meaning “reason.” While the Latin ratio is also the forebear of the English noun ration, referring to a share of something, rationale has nothing to do with a tankard (or stein, or even a pony) of beer.

Merriam-Webster's Word of the Day for September 17, 2025 is:

jovial • \JOH-vee-ul\  • adjective

Jovial describes people as well as moods, attitudes, etc., that are cheerful and jolly. 

// The audience was in a jovial mood as the headlining comedian walked onto the stage.

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Examples:

"Transport yourself to a sumptuous hidden garden somewhere in Europe, where the meats are plentiful and the specials oh so tantalizing. The rustic communal tables and jovial service will make you feel like you're hanging out with your extended family in the old country." — Briony Smith, The Toronto Star, 29 Mar. 2025

Did you know?

In ancient Roman astrology, people were thought to share the personality traits of the god whose planet was rising when they were born. The largest planet was named after the chief Roman god Jupiter, also called Jove. Jove was a sky god and a bringer of light, as well as a great protector who kept heroes focused on being loyal to the gods, the state, and family. Ancient mythology is full of stories of Jupiter (Zeus in the Greek myths) behaving badly, but jovial points only to the joy and happiness of a supremely powerful god: it describes the cheerful and jolly among us. (Jovian is the adjective that describes what is simply related to Jove/Jupiter.) Jovial has historically been contrasted with saturnine, which describes those with a gloomy or surly disposition. Sad Saturn was the father of Jupiter and his siblings, and he was exiled (understandably) for swallowing them all.

Merriam-Webster's Word of the Day for September 16, 2025 is:

debunk • \dee-BUNK\  • verb

To debunk something (such as a belief or theory) is to show that it is not true.

// The influencer remained enormously popular despite having the bulk of their health claims thoroughly debunked.

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Examples:

“Conspiracy theorists (and those of us who argue with them have the scars to show for it) often maintain that the ones debunking the conspiracies are allied with the conspirators.” — Adam Gopnik, The New Yorker, 24 Mar. 2025

Did you know?

To debunk something is to take the bunk out of it—that bunk being nonsense. (Bunk is short for the synonymous bunkum, which has political origins.) Debunk has been in use since at least the 1920s, and it contrasts with synonyms like disprove and rebut by suggesting that something is not merely untrue but is also a sham—a trick meant to deceive. One can simply disprove a myth, but if it is debunked, the implication is that the myth was a grossly exaggerated or foolish claim.