folly

American  

[fol-ee] / ˈfɒl i /

noun

follies plural

1. the state or quality of being foolish; lack of understanding or sense.

2. a foolish action, practice, idea, etc.; absurdity.

   the folly of performing without a rehearsal.

   Synonyms:

   lunacy, madness, injudiciousness, indiscretion, foolishness, mistake, rashness, imprudence

3. a costly and foolish undertaking; unwise investment or expenditure.

4. Architecture. a whimsical or extravagant structure built to serve as a conversation piece, lend interest to a view, commemorate a person or event, etc.: found especially in England in the 18th century.

5. follies, a theatrical revue.

6. Obsolete. wickedness; wantonness.

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folly British  

/ ˈfɒlɪ /

noun

1. the state or quality of being foolish; stupidity; rashness

2. a foolish action, mistake, idea, etc

3. a building in the form of a castle, temple, etc, built to satisfy a fancy or conceit, often of an eccentric kind

4. (plural) theatre an elaborately costumed revue

5. archaic

   1. evil; wickedness

   2. lewdness; wantonness

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Usage

What does folly mean? A folly is a foolish action. Follies can refer to various unwise practices, buildings with a purely ornamental purpose, or cabaret-style theatrical revues featuring lots of beautiful, dancing women.

Other Word Forms

Derived Forms

• superfolly
  noun

Inflected Forms

noun

• follies
  plural

Etymology

Origin of folly

First recorded in 1175–1225; Middle English folie, from Old French, derivative of fol, fou “foolish, mad”; equivalent to fool ¹ + -y ³ ( def. )

Explanation

Folly is a noun that means "foolish or crazy behavior." It would be folly to spend all night playing video games when you have a difficult exam the next day. Folly comes from the Old French word folie meaning "madness, stupidity." It can describe the silly or nonsensical things you do, like the folly of trying to rush across town in the middle of a snowstorm. Or it can describe the trait that makes people act that way: the folly of an inexperienced driver who doesn't know you can't speed on snow-covered roads. Can you see the word fool in folly? Not a coincidence.

Example Sentences

Perhaps Thucydides had something to say about the folly of war that they wouldn’t have appreciated had they remained civilians.

From Salon • Apr. 19, 2026

Ms. Allen concedes their regionalism but argues that they were wiser for understanding that a “provincial backwater offers as full a panoply of human folly, nobility, tragedy, and absurdity as any great metropolis.”

From The Wall Street Journal • Jan. 23, 2026

It also sets up the acute psychology that drives Magellan: obsessive curiosity warping into enforced Christian conversion, a consequential folly to which the filmmaker adds his own historical take.

From Los Angeles Times • Jan. 9, 2026

It would be folly not to look at the opportunity cost of taking that $45,000 from your IRA.

From MarketWatch • Jan. 9, 2026

From here, lit by starlight, I can see the maze below and the folly in the center.

From "The Cruel Prince" by Holly Black

Related Words

• absurdity
• craziness
• foolishness
• idiocy
• indiscretion
• lunacy
• madness
• recklessness
• silliness
• stupidity