1.
irrational; contrary to reason; not conforming to rational principles
Describes behavior, beliefs, systems, or decisions that go against reason or rational judgment. Frequently used in economics, psychology, and philosophy to label actions that maximize neither efficiency nor logic. The direct antonym is 合理的 ('rational; reasonable').
非合理的な行動。
Irrational behavior.
Formed with the negating prefix 非 ('non-; un-') attached to 合理的 ('rational'). It points to a lack of reasoned grounds rather than to simple wrongness or illegality.
Usage
- Used as a な-adjective: 非合理的な制度 ('an irrational system').
- Adverbially: 非合理的に振る舞う ('to act irrationally').
- Common in academic and journalistic writing; in casual speech, おかしい ('weird') or 意味がない ('meaningless') may be more natural.
- In behavioral economics, the phrase 人間の非合理性 ('human irrationality') is frequent.
Common collocations
- 非合理的な行動: irrational behavior
- 非合理的な判断: irrational judgment
- 非合理的な制度: irrational system
- 非合理的な信念: irrational belief
- 非合理的に感じる: to feel unreasonable
Similar words
- 合理的: rational; reasonable — the direct antonym.
- 非論理的: illogical — focuses on reasoning that does not follow valid logical steps, rather than on overall unreasonableness.
- 不合理: unreasonable; irrational — very close in meaning; 不合理 often functions as a noun or な-adjective stem and tends to be slightly more formal.
- 理不尽: unreasonable; unjust — emphasizes unfairness and treatment of others, not cognitive irrationality.