irrational
/ɪˈræʃ.ən.əl/- 1.
Not guided by logic or clear reasoning. Used to describe thoughts, feelings, or actions that don't make sense when examined carefully.
- Her irrational fear of buttons made everyday life difficult.
- Quitting without a plan seemed like an irrational decision.
- Don't let irrational thoughts stop you from trying new things.
- 2.
In mathematics, an irrational number cannot be written as a simple fraction. It has a decimal that goes on forever without repeating.
- Pi is an irrational number used constantly in geometry.
- The square root of 2 is irrational — it never ends or repeats.
Adinary Nuance
"Irrational," "unreasonable," and "illogical" are close neighbors, but each has a different focus. "Unreasonable" is mainly about attitude or demands — a boss who refuses any compromise is unreasonable. "Illogical" targets a specific flaw in an argument — when a conclusion simply doesn't follow from the evidence given. "Irrational" is the broadest of the three: it covers any thought, feeling, or behavior that goes against reason, including deep emotional reactions. So a person's phobia is "irrational," a manager's refusal to negotiate is "unreasonable," and a poorly built argument is "illogical." In IELTS writing, choosing the right word here signals precision to the examiner.
In other languages
- Vietnamese
- Phi lý
- Spanish
- Irracional
- Chinese
- 不理性的
- Japanese
- 不合理な
- Korean
- 비이성적인
Etymology
From Latin *irrationalis* ("without reason"), formed by adding *ir-* (a variant of "not") to *rationalis* ("of reason, logical"). The word entered English in the late 15th century.
Common phrases
Synonyms
Related words
Frequently asked questions
- What is the difference between 'irrational' and 'unreasonable'?
- 'Unreasonable' describes a person or demand that is unfair or unwilling to listen — it's about attitude. 'Irrational' means going against logic or reason — it's about the nature of the thinking itself, often including uncontrollable emotions.
- Is 'irrational' formal or can I use it in everyday speech?
- 'Irrational' works in both registers. You'll find it in IELTS essays and academic papers, but it's also natural in conversation — for example, 'I know it's irrational, but I'm scared anyway.'
- Is it rude to call someone 'irrational'?
- It can sound dismissive in direct conversation. It's safer to describe the specific behavior rather than the person — say 'that fear seems irrational' rather than 'you're being irrational,' especially in a formal or professional setting.
- How is 'irrational' used in IELTS or academic writing?
- In academic writing, 'irrational' often describes decision-making, beliefs, or fears that lack logical basis. For example: 'Consumers sometimes make irrational choices based on emotion rather than evidence.' It is a precise, well-regarded word at this level.