Merriam-Webster's Word of the Day for August 14, 2025 is:

immutable • \ih-MYOO-tuh-bul\  • adjective

Immutable is a formal adjective used to describe something that is unable to be changed.

// It is hardly an immutable fact that cats and dogs are sworn enemies; over the years our golden retriever has grown both fond and protective of her tabby housemate.

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Examples:

“... by the 1800s, naturalists like Lamarck were questioning the assumption that species were immutable; they suggested that over time organisms actually grew more complex, with the human species as the pinnacle of the process. Darwin brought these speculations into public consciousness in 1859 with On the Origin of Species, and while he emphasized that evolution branches in many directions without any predetermined goal in mind, most people came to think of evolution as a linear progression.” — Ted Chiang, LitHub.com, 6 Mar. 2025

Did you know?

Immutable may describe something that is incapable of change, but the word itself—like all words—is mutable, both capable of and prone to alteration. To put a finer point on it, if language were fixed, we wouldn't have immutable itself, which required a variety of mutations of the Latin verb mutare (“to change”) to reach our tongues (or pens, keyboards, or touchscreens—oh the many permutations of communication!). Other English words that can be traced back to mutare include mutate, transmute, and commute. Which reminds us—the mutability of language makes great food for thought during one's commute.

Merriam-Webster's Word of the Day for August 13, 2025 is:

calculus • \KAL-kyuh-lus\  • noun

Calculus refers to an advanced branch of mathematics that deals mostly with rates of change and with finding lengths, areas, and volumes. The word can also be used more broadly for the act of calculating—that is, estimating something by using practical judgment, or solving or probing the meaning of something.

// By my calculus the more efficient air conditioner will have paid for itself within a span of five years.

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Examples:

“[Manager, Craig] Counsell said that all options are being considered, and the Cubs will wait to make a decision until they have to, as events between now and [Shota] Imanaga's official return to the active roster could change the calculus.” — Vinnie Duber, The Chicago Sun-Times, 21 June 2025

Did you know?

Solving calculus equations on a chalkboard allows one to erase mistakes, and also hints at the word's rocky, and possibly chalky, past. Calculus entered English in the 17th century from Latin, in which it referred to a pebble, often one used specifically for adding and subtracting on a counting board. The word thus became associated with computation; the phrase ponere calculos, literally, “to place pebbles,” meant “to carry out a computation.” The Latin calculus, in turn, is thought to perhaps come from the noun calx, meaning “lime” or “limestone,” which is also the ancestor of the English word chalk. Today, in addition to referring to an advanced branch of mathematics, calculus can also be used generally for the act of solving or figuring something out, and as a medical term for the tartar that forms on teeth, among other things. Whichever way it's used, we think that calculus rocks.

Merriam-Webster's Word of the Day for August 12, 2025 is:

ramshackle • \RAM-shak-ul\  • adjective

Ramshackle describes things that are in a very bad condition and need to be repaired, or that are carelessly or loosely constructed.

// Toward the back of the property stood a ramshackle old shed.

// The book had a ramshackle plot that was confusing and unbelievable.

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Examples:

"House of the Weedy Seadragon ... and Semaphore Shack sit side-by-side in the sand dunes. They're part of a cosy cluster of ramshackle residences, built in the 1930s by a Hobart family as weekenders for the extended tribe to fish, swim and while away sun-soaked days." — The Gold Coast (Australia) Bulletin, 4 July 2025

Did you know?

Ramshackle has nothing to do with rams, nor the act of being rammed, nor shackles. The word is an alteration of ransackled, an obsolete form of the verb ransack, meaning "to search through or plunder." (Ransack comes from Old Norse rannsaka, which combines rann, "house," and -saka, a relation of the Old English word sēcan, "to seek.") A home that has been ransacked has had its contents thrown into disarray, and that image may be what inspired people to start using ramshackle in the first half of the 19th century to describe something that is poorly constructed or in a state of near collapse. Ramshackle in modern use can also be figurative, as in "a ramshackle excuse for the error."

Merriam-Webster's Word of the Day for August 11, 2025 is:

stipulate • \STIP-yuh-layt\  • verb

To stipulate is to demand or require something as part of an agreement.

// The rules stipulate that players must wear uniforms.

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Examples:

“Nilsson's reputation preceded her. The New York Times wrote of her: ‘Christine Nilsson, the Met's first diva in 1883, could not only stipulate by contract her choice of roles, but could prohibit their performance by any other soprano in the same season.'” — Elise Taylor and Stephanie Sporn, Vogue, 20 June 2025

Did you know?

Like many terms used in the legal profession, stipulate, an English word since the 17th century, has its roots in Latin. It comes from stipulatus, the past participle of stipulari, a verb meaning “to demand a guarantee (from a prospective debtor).” In Roman law, oral contracts were deemed valid only if they followed a proper question-and-answer format; stipulate was sometimes used specifically of this same process of contract making, though it also could be used more generally for any means of making a contract or agreement. The “to specify as a condition or requirement” meaning of stipulate also dates to the 17th century, and is the sense of the word most often encountered today.

Merriam-Webster's Word of the Day for August 10, 2025 is:

hidebound • \HYDE-bound\  • adjective

Someone or something described as hidebound is inflexible and unwilling to accept new or different ideas.

// Although somewhat stuffy and strict, the professor did not so completely adhere to hidebound academic tradition that he wouldn't teach class outside on an especially lovely day.

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Examples:

“He was exciting then, different from all the physicists I worked with in the way that he was so broadly educated and interested, not hidebound and literal, as my colleagues were.” — Joe Mungo Reed, Terrestrial History: A Novel, 2025

Did you know?

Hidebound has its origins in agriculture. The adjective, which appeared in English in the early 17th century, originally described cattle whose skin, due to illness or poor feeding, clung to the skeleton and could not be pinched, loosened, or worked with the fingers (the adjective followed an earlier noun form referring to this condition). Hidebound was applied to humans too, to describe people afflicted with tight skin. Figurative use quickly followed, first with a meaning of “stingy” or “miserly.” That sense has since fallen out of use, but a second figurative usage, describing people who are rigid or unyielding in their actions or beliefs, lives on in our language today.

Merriam-Webster's Word of the Day for August 9, 2025 is:

behemoth • \bih-HEE-muth\  • noun

A behemoth is something of monstrous size, power, or appearance. Behemoth (usually capitalized) is also the name of a mighty animal described in the biblical book of Job.

// The town will be voting on whether or not to let the retail behemoth build a store on the proposed site.

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Examples:

"The author ... recounts how his grandfather turned a family spinach farm into an industrial behemoth, and exposes the greed and malfeasance behind the prosperous facade." — The New York Times, 6 July 2025

Did you know?

In the biblical book of Job, Behemoth is the name of a powerful grass-eating, river-dwelling beast with bones likened to bronze pipes and limbs likened to iron bars. Scholars have speculated that the biblical creature was inspired by the hippopotamus, but details about the creature's exact nature are vague. The word first passed from the Hebrew word bĕhēmōth into Late Latin (the Latin used by writers in the third to sixth centuries), where, according to 15th century English poet and monk John Lydgate it referred to "a beast rude full of cursednesse." In modern English, behemoth functions as an evocative term for something of monstrous size, power, or appearance.

Merriam-Webster's Word of the Day for August 8, 2025 is:

winsome • \WIN-sum\  • adjective

Winsome describes people and things that are cheerful, pleasant, and appealing.

// Though a relative newcomer to acting, Maya won the casting directors over with her winsome charm, which was perfect for the role of the plucky young superhero.

// Our winsome guide put us at ease immediately.

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Examples:

“Wilson's take on Snow White is surprisingly winsome. It delivers a familiar story with a fresh perspective and some unexpected sources of nostalgia.” — Kristy Puchko, Mashable, 19 March 2025

Did you know?

Despite appearances, winsome bears no relation to the familiar word win, meaning “to achieve victory.” The Old English predecessor of winsome is wynsum, which in turn comes from the noun wynn, meaning “joy” or “pleasure.” And the ancestor of win is the Old English verb winnan, meaning “to labor or strive.” Given those facts, one might guess that the adjective winning, meaning “tending to please or delight,” as in “a winning personality,” is a winsome relation, but in fact it's in the win/winnan lineage. Winning is more common today than the similar winsome in such constructions as “a winning/winsome smile,” but we sense no hard feelings between the two. It's just the way things (lexically) go: you win some, you lose some.

Merriam-Webster's Word of the Day for August 7, 2025 is:

adjudicate • \uh-JOO-dih-kayt\  • verb

To adjudicate a dispute between two parties is to make an official decision about which party is right; to adjudicate a case or claim is to settle it judicially. Adjudicate is also used to mean “to act as judge.”

// The case will be adjudicated in the state courts.

// The property title cannot be transferred until a case concerning the affected rights of way is adjudicated.

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Examples:

“… [Pete] Rose's candidacy won't be adjudicated on the writers' ballot. According to the Hall's voting rules, players who are retired for more than 15 years are considered not by 400-plus writers but rather a smaller ‘era committee,' comprised of a mixture of former players, executives, and media members.” — Scott Lauber, The Philadelphia Inquirer, 14 May 2025

Did you know?

Adjudicate, which is usually used to mean “to make an official decision about who is right in a dispute,” is one of several terms that give testimony to the influence of jus, the Latin word for “law,” on our legal language. Others include judgment, judicial, prejudice, jury, justice, injury, and perjury. What's the verdict? Latin “law” words frequently preside in English-speaking courtrooms.

Merriam-Webster's Word of the Day for August 6, 2025 is:

largesse • \lahr-ZHESS\  • noun

Largesse is a somewhat formal word that refers to the act of giving away money or the generosity of a person who gives away money. It can also refer to the money that is given away.

// The community has benefited greatly from the largesse of its wealthiest family.

// The local business owner is a philanthropist known for his largesse.

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Examples:

"Over the years, ShelterBox USA, an outgrowth of the Rotary Club and named for the relief boxes it distributes, has helped nearly 3 million people in some of the world's worst disaster zones. It hands out basic survival needs: tents, tools, and household supplies. Twice the organization has been nominated for the Nobel Peace Prize for its life-preserving largesse." — The Olney (Texas) Enterprise, 20 Mar. 2025

Did you know?

The English language has benefited from the largesse of Anglo-French, through which a generous number of words have passed; examples range from simple to account to desert. English speakers owe Anglo-French a huge thanks, in particular, for its adjective large. That word, meaning "generous, broad, or wide," is the source of both largesse and the familiar duo of large and enlarge. Most people understand enlarge to mean "to make larger," but a less common sense (used in Shakespeare's Henry V) is "to set free." Largesse also contains the notion of freedom, specifically with regard to a lack of financial constraints: it's not about having a "large" amount of money but rather being "free" with it. Incidentally, the English word large wasn't about size when it was first adopted in the 13th century. Back then it meant "lavish."

Merriam-Webster's Word of the Day for August 5, 2025 is:

contentious • \kun-TEN-shuss\  • adjective

Contentious describes something that is likely to cause people to argue or disagree or that involves a lot of arguing. When used of a person, contentious describes someone likely or willing to argue.

// I think it's wise to avoid such a contentious topic at a dinner party.

// After a contentious debate, members of the committee finally voted to approve the funding.

// The dispute involves one of the region's most contentious leaders.

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Examples:

“Next up will be Peter Shaffer's ‘Amadeus,' which opened in 1979 and won the Tony for best play in 1981 with Ian McKellen winning lead actor honors. ... The story is a fictional account of the contentious relationship between Wolfgang Amadeus Mozart and his rival, Antonio Salieri, the court composer of the Austrian emperor.” — Jessica Gelt, The Los Angeles Times, 12 June 2025

Did you know?

If everyone has a bone to pick now and then, contentious types have entire skeletons. While English has plenty of words for people prone to fighting—combative and belligerent among them—contentious implies a fondness for arguing that others find particularly tedious or wearying. Thankfully, even the most contentious cranks and crabs among us have no cause to quibble over the history of the word contentious, as its origins are very clear: contentious comes (by way of Middle French) from the Latin adjective contentiōsus, meaning “persistent, obstinate, argumentative, or quarrelsome.”