Quantcast
Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary

fallacy

play
noun fal·la·cy \ˈfa-lə-sē\

Simple Definition of fallacy

  • : a wrong belief : a false or mistaken idea

  • : the quality of being false or wrong

Source: Merriam-Webster's Learner's Dictionary

Full Definition of fallacy

plural

fallacies

  1. 1 a obsolete :  guile, trickery b :  deceptive appearance :  deception

  2. 2 a :  a false or mistaken idea <popular fallacies> b :  erroneous character :  erroneousness

  3. 3 :  an often plausible argument using false or invalid inference

Examples of fallacy in a sentence

  1. The fallacy of their ideas about medicine soon became apparent.

  2. <the once-common fallacy that girls just weren't any good at math>



Origin and Etymology of fallacy

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


First Known Use: 14th century

Rhymes with fallacy


FALLACY Defined for Kids

fallacy

play
noun fal·la·cy \ˈfa-lə-sē\

Definition of fallacy for Students

plural

fallacies

  1. 1 :  a false or mistaken idea

  2. 2 :  false reasoning





Seen and Heard

What made you want to look up fallacy? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

to take off or remove

Get Word of the Day daily email!

WORD GAMES

Take a 3-minute break and test your skills!

confounded-person

Which is a synonym of indolent?

lazy philistine melancholy frenetic
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ