Definition of fallacy in English:

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Pronunciation: /ˈfaləsē/

noun (plural fallacies)

1A mistaken belief, especially one based on unsound argument: the notion that the camera never lies is a fallacy
More example sentences
  • What binds all these things together is a recurring human mistake: the fallacy of total belief in the present and its technology.
  • I can't summon the necessary faith to believe in magic if I suspect it's inconsistent nonsense, or a mess of superstitions based on fallacies.
  • It is based on myths and fallacies which provide legitimacy for gross social inequalities.
misconception, misbelief, delusion, mistaken impression, error, misapprehension, misinterpretation, misconstruction, mistake;
untruth, inconsistency, myth
1.1 Logic A failure in reasoning that renders an argument invalid.
Example sentences
  • Finally, yet another theory of fallacy says a fallacy is a failure to provide adequate proof for a belief, the failure being disguised to make the proof look adequate.
  • So the knowledge argument is invalid because it involves a fallacy of equivocation: ‘know’ means something different in the two premises.
  • Dretske has denied that knowledge is closed under implication; further, he has diagnosed closure as the fallacy that drives arguments for scepticism.
1.2Faulty reasoning; misleading or unsound argument: the potential for fallacy which lies behind the notion of self-esteem
More example sentences
  • I was under the impression that this was a forum where political issues could be discussed rationally: if you want me to be pedantic and point out every logical fallacy in every reply I've received then I'll do that.
  • Predictably, the appeal to personal experience is another well-known logical fallacy.
  • The little logical fallacy that bugged me the most was the scene where the earthquake followed the Amtrak train.


Late 15th century (in the sense 'deception, guile'; gradually superseding Middle English fallace): from Latin fallacia, from fallax, fallac- 'deceiving', from fallere 'deceive'.

For editors and proofreaders

Syllabification: fal·la·cy

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