iˌrratioˈnality
C1Formal
Definition
Meaning
The quality or state of being illogical or unreasonable; acting without clear thought or reason.
A belief, action, or condition that is inconsistent with logical reasoning, often influenced by emotion, bias, or instinct rather than evidence or deliberate calculation. In mathematics, refers to a real number that cannot be expressed as a ratio of integers (e.g., π, √2).
Linguistics
Semantic Notes
Primarily an uncountable noun describing a quality or state. Can be used countably in plural ('irrationalities') to refer to specific instances or examples of irrational behaviour or beliefs.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage. Spelling is consistent.
Connotations
In both varieties, strongly implies a deviation from expected logical norms, often with a negative judgment. In philosophical contexts, it is a neutral technical term.
Frequency
Slightly more frequent in academic and philosophical texts than in everyday conversation in both dialects.
Vocabulary
Collocations
Grammar
Valency Patterns
[irrationality of + NP][irrationality + clause][Adj + irrationality]Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “a triumph of hope over rationality (variation)”
Usage
Context Usage
Business
Used to criticise market behaviour or corporate decisions not based on data, e.g., 'The market's volatility reflects pure irrationality.'
Academic
A key term in philosophy, psychology, and behavioural economics, e.g., 'The study explores the cognitive roots of human irrationality.'
Everyday
Used to describe frustrating or baffling behaviour, e.g., 'The irrationality of the new parking rules is infuriating.'
Technical
In mathematics, a property of numbers, e.g., 'The proof demonstrated the irrationality of √2.'
Examples
By Part of Speech
verb
British English
- To irrationalise (rare, non-standard).
American English
- To irrationalize (rare, non-standard).
adverb
British English
- He behaved irrationally during the debate.
American English
- The market reacted irrationally to the minor news.
adjective
British English
- His fears were completely irrational.
American English
- Her reaction seemed irrational to the committee.
Examples
By CEFR Level
- His sudden anger showed a moment of irrationality.
- The government's policy was criticised for its economic irrationality.
- The philosopher argued that a degree of irrationality is essential to the human condition, challenging purely utilitarian models of behaviour.
Learning
Memory Aids
Mnemonic
Think: 'IRRAtionalITY' – When an IRA (Irish Republican Army) decision seems crazy? No, it's irrational. (Note: This is a purely phonetic mnemonic, not a political statement.)
Conceptual Metaphor
IRRATIONALITY IS A FORCE (e.g., 'swept away by irrationality'), IRRATIONALITY IS DARKNESS/OBSCURITY (e.g., 'descended into irrationality'), IRRATIONALITY IS A DISEASE (e.g., 'a contagion of irrationality').
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'irrational number' (иррациональное число) when the meaning is behavioural. The behavioural term is 'нерациональность' or, more commonly, 'неразумность', 'нелогичность'.
Common Mistakes
- Confusing 'irrationality' (state/quality) with 'an irrationality' (a single instance). Using 'irrational' (adj.) where the noun form is needed. Misspelling as 'irationality' (missing one 'r').
Practice
Quiz
In which context is 'irrationality' used as a precise, non-judgmental technical term?
FAQ
Frequently Asked Questions
Most often yes, implying a fault. However, in some philosophical or artistic contexts, it can be neutral or even positive, suggesting freedom from rigid logic.
Yes, the plural 'irrationalities' is used to refer to specific instances or examples of irrational behaviour or beliefs (e.g., 'the various irrationalities of the old system').
'Irrationality' is stronger and more fundamental, suggesting a failure of logical thought. 'Unreasonableness' can be softer, often about being unfair or unwilling to listen to reason, not necessarily incapable of logic.
The primary stress is on '-nal-' (/ˈnæl/). There is a secondary stress on the first syllable 'ir-' (/ɪˌræʃ/). Practice saying 'IR-rash-i-NAL-i-tee' slowly to feel the stress pattern.