fal·​la·​cy | \ ˈfa-lə-sē How to pronounce fallacy (audio) \
plural fallacies

Essential Meaning of fallacy

1 : a wrong belief : a false or mistaken idea popular fallacies about medicine It's a fallacy (to believe) that the Earth is flat.
2 : the quality of being false or wrong The fallacy of their ideas about medicine soon became apparent.

Full Definition of fallacy

1a : a false or mistaken idea popular fallacies prone to perpetrate the fallacy of equating threat with capability— C. S. Gray
b : erroneous character : erroneousness The fallacy of their ideas about medicine soon became apparent.
2a : deceptive appearance : deception
b obsolete : guile, trickery
3 : an often plausible argument using false or invalid inference

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Did you know?

Philosophers are constantly using the word fallacy. For them, a fallacy is reasoning that comes to a conclusion without the evidence to support it. This may have to do with pure logic, with the assumptions that the argument is based on, or with the way words are used, especially if they don't keep exactly the same meaning throughout the argument. There are many classic fallacies that occur again and again through the centuries and everywhere in the world. You may have heard of such fallacies as the "ad hominem" fallacy, the "question-begging" fallacy, the "straw man" fallacy, the "slippery slope" fallacy, the "gambler's" fallacy, or the "red herring" fallacy. Look them up and see if you've ever been guilty of any of them.

Examples of fallacy in a Sentence

The fallacy of their ideas about medicine soon became apparent. the once-common fallacy that girls just weren't any good at math
Recent Examples on the Web The idea that local problems are uniquely insurmountable is a fallacy that can be corrected by experiencing how others have experienced and solved similar issues. Ricardo Villadiego, Forbes, 28 Sep. 2021 One obvious fallacy when people generalize about the European model is that there isn’t one model, but several. Timothy Noah, The New Republic, 8 Sep. 2021 Their lives stand in stark contrast to the feel-good fallacy that Canada is inherently good or safe or superior to our neighbours south of the border. Kathleen Newman-bremang, refinery29.com, 30 July 2021 This is a logical fallacy known as begging the question. Teddy Mcdarrah, Forbes, 28 June 2021 Meanwhile, the fallacy of undervaluing STARS workers has been on full display throughout the Covid-19 pandemic. Sarah Todd, Quartz, 13 Aug. 2021 But while this fallacy is well known in economics, sunk costs are a big deal in the practical world of politics. Sean-michael Pigeon, National Review, 7 June 2021 Age of Majority’s research underscores the fallacy of such efforts. Charles Taylor, Forbes, 4 May 2021 All of that is a mix of fallacy and wishful thinking. Washington Post, 10 Aug. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'fallacy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of fallacy

15th century, in the meaning defined at sense 2b

History and Etymology for fallacy

Latin fallacia, from fallac-, fallax deceitful, from fallere to deceive

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Time Traveler for fallacy

Time Traveler

The first known use of fallacy was in the 15th century

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Dictionary Entries Near fallacy



fallacy of accident

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Statistics for fallacy

Last Updated

25 Oct 2021

Cite this Entry

“Fallacy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fallacy. Accessed 28 Oct. 2021.

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More Definitions for fallacy


fal·​la·​cy | \ ˈfa-lə-sē How to pronounce fallacy (audio) \
plural fallacies

Kids Definition of fallacy

1 : a false or mistaken idea
2 : false reasoning

More from Merriam-Webster on fallacy

Nglish: Translation of fallacy for Spanish Speakers

Britannica English: Translation of fallacy for Arabic Speakers

Britannica.com: Encyclopedia article about fallacy


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