illogical

C2+ Topic:Senses & Perception

US /ɪˈlɑdʒɪkəl/ UK /ɪˈlɒdʒɪkəl/ See IPA manual

Meanings

1

adj
lacking sound reasoning; contrary to logic

His conclusion was illogical given all the evidence.

Thesaurus

Synonyms

1 adj · lacking sound reasoning;... irrational unreasonable absurd incoherent fallacious unsound

Opposites

logical rational coherent reasonable

Word family

Derived forms illogicallyillogicality

Related forms logical logic

Etymology

From in- ('not') + logical, from Late Latin logicus, from Ancient Greek logikos ('of reasoning'), from logos ('word, reason').

logikos Ancient Greek logos Ancient Greek

View etymology graph ->

Topics

Senses & Perception Word Formation & Derivatives

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# illogical

**Type:** Word
**Level:** C2+
**Part of speech:** adj
**IPA (US):** /ɪˈlɑdʒɪkəl/
**IPA (UK):** /ɪˈlɒdʒɪkəl/

## Meanings
1. lacking sound reasoning; contrary to logic

## Examples
- His conclusion was illogical given all the evidence.

## Synonyms
- irrational
- unreasonable
- absurd
- incoherent
- fallacious
- unsound

## Antonyms
- logical
- rational
- coherent
- reasonable

## Derived Forms
- illogically
- illogicality

## Related Forms
- logical
- logic

## Roots and Affixes
- Root: logikos
- Root: logos
- Affix: il- - not

## Etymology
From in- ('not') + logical, from Late Latin logicus, from Ancient Greek logikos ('of reasoning'), from logos ('word, reason').

## AI Etymology
illogical comes from in- ('not') + logical, from Late Latin logicus, from Ancient Greek logikos ('of reasoning'), from logos ('word, reason'). Morphologically, the prefixed shape matters: the initial element belongs to the recorded formation and helps explain the modern form's surface analysis. In present English, the adjective sense is "lacking sound reasoning; contrary to logic", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as logical and logic, and in derivatives such as illogically and illogicality. Its semantic neighborhood includes irrational, unreasonable, absurd, and incoherent, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Ancient Greek logikos and Ancient Greek logos.

## Topics
- Senses & Perception
- Word Formation & Derivatives

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illogical

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