fallacy

C2 Topic:Philosophy & Reasoning

US /ˈfɛl.ə.si/ UK /ˈfæl.ə.si/ See IPA manual

Freq #43048

Meanings

1

noun
A mistaken belief based on faulty reasoning.

It is a common fallacy that money always brings happiness.
2

noun
A flawed argument that seems convincing but is actually invalid.

His conclusion rested on a logical fallacy that the professor quickly exposed.

Thesaurus

Synonyms

1 noun · a mistaken belief based on... false beliefmisconception

2 noun · a flawed argument that... logical fallacy

Word family

Forms fallacies

Derived forms counterfallacyfallaciousphallusy

Related forms fail fallible sophism

Appears in

Phrases (1)

See all

pathetic fallacy
the attribution of human feelings to natural phenomena or inanimate objects

Adjective + noun

Etymology

From Middle English fallaci, fallace, fallas, from Old French fallace, from Latin fallācia (“deception, deceit”), from fallāx (“deceptive, deceitful”), from fallere (“to deceive”).

fallaci Middle English fallace Old French fallācia Latin

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Topics

Philosophy & Reasoning Abstract Ideas Word Formation & Derivatives

External links

# fallacy

**Type:** Word
**Level:** C2
**Part of speech:** noun
**IPA (US):** /ˈfɛl.ə.si/
**IPA (UK):** /ˈfæl.ə.si/
**Frequency rank:** 43048

## Meanings
1. A mistaken belief based on faulty reasoning.
2. A flawed argument that seems convincing but is actually invalid.

## Examples
- It is a common fallacy that money always brings happiness.
- His conclusion rested on a logical fallacy that the professor quickly exposed.

## Derived Forms
- counterfallacy
- fallacious
- phallusy

## Related Forms
- fail
- fallible
- sophism

## Roots and Affixes
- Root: fallaci
- Root: fallace
- Root: fallācia

## Etymology
From Middle English fallaci, fallace, fallas, from Old French fallace, from Latin fallācia (“deception, deceit”), from fallāx (“deceptive, deceitful”), from fallere (“to deceive”).

## AI Etymology
Fallacy is from Middle English fallaci, fallace, fallas, from Old French fallace, from Latin fallācia (“deception, deceit”), from fallāx (“deceptive, deceitful”), from fallere (“to deceive”). Important recorded forms include fallaci (Middle English), fallace (Old French), and fallācia (Latin). Current senses include a mistaken belief based on faulty reasoning and a flawed argument that seems convincing but is actually invalid. The wider family includes derived forms such as counterfallacy, fallacious, and phallusy; related words such as fail, fallible, and sophism.

## Topics
- Philosophy & Reasoning
- Abstract Ideas
- Word Formation & Derivatives

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