adjective

fallacious

fuh-LAY-shuss

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Fallacious (adjective) means Based on faulty reasoning or a mistaken belief, and therefore wrong. Example: “The argument that prices always fall in a recession is fallacious.”

adjective

formal Based on faulty reasoning or a mistaken belief, and therefore wrong.

"The argument that prices always fall in a recession is fallacious."

"She exposed the fallacious assumption at the heart of the report."

formal Likely to mislead someone, whether or not deliberately.

"The advert made fallacious claims about the product's health benefits."

How to use fallacious

Learner’s notes

In plain EnglishWrong because the thinking behind it does not hold up.

When to use it

Formal. Most at home in academic writing, philosophy, law and argument analysis; in everyday speech people usually just say wrong or misleading.

Memory tip

The noun is fallacy, and the adverb is fallaciously. A fallacious argument contains a fallacy.

Trace the full origin ↓

Easily confused with

fallible → fictitious → fraudulent →

Common pairings

fallacious argument fallacious reasoning fallacious assumption patently fallacious

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

Test yourself on “fallacious” A quick quiz — meaning, synonyms & usage →

Fill the gap

Can you complete this real example?

The argument that prices always fall in a recession is _____.

Etymology

From Latin fallax, fallac- 'deceitful', from fallere 'to deceive'. The same root gives English fail, fault and false.

Origin: Latin

Synonyms

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unsound erroneous illogical specious spurious misleading deceptive false deceitful fraudulent

Antonyms

sound valid logical truthful accurate

Related words

not right true wrong sound slow correct false

Rhymes for fallacious

yous nous heinous ominous curious anxious copious tenuous unctuous tortuous spurious infamous

See all rhymes for fallacious →

Frequently asked questions

What is the difference between fallacious and false?

False simply means untrue, whereas fallacious means the reasoning used to reach a conclusion is defective. A fallacious argument can even reach a true conclusion by bad logic, and a false statement can be made without any argument at all.

What is the difference between fallacious and fallible?

Fallacious describes an argument or belief that is logically unsound. Fallible describes a person or system that is capable of making mistakes. People are fallible; their arguments may be fallacious.

Is fallacious the adjective of fallacy?

Yes. A fallacy is a flaw in reasoning, and fallacious is the adjective describing anything that contains one, such as a fallacious claim or a fallacious line of argument.

What is the meaning of fallacious?

"fallacious" (adjective) means based on faulty reasoning or a mistaken belief, and therefore wrong.

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