fallacy

[ fal-uh-see ]

noun

, plural fal·la·cies.

1. a deceptive, misleading, or false notion, belief, etc.:

   That the world is flat was at one time a popular fallacy.

   Synonyms: misapprehension, delusion, misconception

2. a misleading or unsound argument.
3. deceptive, misleading, or false nature; erroneousness.
4. Logic. any of various types of erroneous reasoning that render arguments logically unsound.
5. Obsolete. deception.

fallacy

/ ˈfæləsɪ /

noun

1. an incorrect or misleading notion or opinion based on inaccurate facts or invalid reasoning
2. unsound or invalid reasoning
3. the tendency to mislead
4. logic an error in reasoning that renders an argument logically invalid

fallacy

1. A false or mistaken idea based on faulty knowledge or reasoning. For example, kings who have divorced their wives for failing to produce a son have held to the fallacy that a mother determines the sex of a child, when actually the father does. ( See sex chromosomes .)

Word History and Origins

Origin of fallacy¹

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

Word History and Origins

Origin of fallacy¹

C15: from Latin fallācia , from fallax deceitful, from fallere to deceive

Example Sentences

Trump's relentless repetition of the zero-sum fallacy, however, has sadly convinced many voters that two groups of people are at odds with each other: men and women.

From Salon

Here are four of his essay’s more obvious fallacies.

From Salon

What he might not have expected was Harris calling out that fallacy.

From Salon

Within the first two hours of the shop opening, the sunk-cost fallacy is in full effect.

From Los Angeles Times

China’s Taiwan Affairs Office denounced Lai for promoting “separatist fallacies” and for advocating Taiwanese independence.

From Los Angeles Times

Related Words

• deception
• falsehood
• heresy
• inconsistency
• misinterpretation
• paradox
• untruth