fallacy
Americannoun
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fallacies
plural
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a deceptive, misleading, or false notion, belief, etc..
That the world is flat was at one time a popular fallacy.
- Synonyms:
- misapprehension, delusion, misconception
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a misleading or unsound argument.
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deceptive, misleading, or false nature; erroneousness.
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Logic. any of various types of erroneous reasoning that render arguments logically unsound.
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Obsolete. deception.
noun
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an incorrect or misleading notion or opinion based on inaccurate facts or invalid reasoning
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unsound or invalid reasoning
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the tendency to mislead
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logic an error in reasoning that renders an argument logically invalid
Other Word Forms
Noun Inflected Forms
Etymology
Origin of fallacy
First recorded in 1350–1400; from Latin fallācia “a trick, deceit,” from fallāc- (stem of fallāx ) “deceitful” + -ia -y 3; replacing Middle English fallace, from Middle French
Explanation
A fallacy is a misleading argument or belief based on a falsehood. If you oppose state testing in schools, you think it is a fallacy that educational quality can be measured by standardized tests. Fallacy comes from the Latin fallacia, for deceit. It technically means a flaw in an argument that makes it deceptive or misleading. In poetry, the "pathetic fallacy" is the false idea that things like rocks or stars have human feelings (pathos). Fallacy can also be used more generally for any false statement or idea. Some synonyms are misconception and error.
Vocabulary lists containing fallacy
Argumentative Writing
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TEKS ELAR Academic Vocabulary List (5th-7th grades)
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Power Suffix: -acy
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
But we know too that to double down is to fall prey to the timeworn seduction of the sunk-cost fallacy: We’ve invested so much in this effort that to abandon it now would be worse.
From The Wall Street Journal ● Aug. 3, 2026
"This is the sunk cost fallacy," he said, adding that "it keeps the addictive behaviour loop".
From Barron's ● May 31, 2026
Loss aversion, sunk-cost fallacy and herd behavior — all of it kicks in during a drawdown.
From MarketWatch ● May 12, 2026
"I think the thing young founders get wrong is they view hours worked in and of itself as necessary and sufficient to think of themselves as productive. And that's where the fallacy lies", he explains.
From BBC ● Feb. 8, 2026
Asserting that De Soto’s visit caused the subsequent collapse of the Caddo and Coosa may be only the old logical fallacy of post hoc ergo propter hoc.
From "1491" by Charles C. Mann
I’m not alleging that Mr. Pelley deploys these fallacies consciously and with self-awareness.
From The Wall Street Journal ● Jun. 9, 2026
“One of the fallacies is that this is only targeting Latinos. If you look at the Vietnamese, Cambodian, Hmong, Chinese, even Japanese communities, they’re being picked up right in court.”
From Los Angeles Times ● Aug. 14, 2025
Here are four of his essay’s more obvious fallacies.
From Salon ● Oct. 31, 2024
So placing that art outside time, or concocting fallacies about its artist’s intentions, has the potential to skew our perception of the art moving forward.
From Slate ● Sep. 1, 2024
“It’s one of the great fallacies, it seems to me,” said Lee, “that time gives much of anything but years and sadness to a man.”
From "East of Eden" by John Steinbeck
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
