Translation guide
The English word 'rational' covers a range of meanings from logical thinking to reasonable behavior. In Japanese, different words and patterns are used depending on whether you mean 'based on reason rather than emotion', 'sensible and practical', or 'able to think clearly'. This guide helps you choose the most natural expression.
Describing a decision, argument, or approach that is logical and not influenced by feelings.
The most common and versatile word for 'rational' in the sense of logical, efficient, and based on reason. Used for decisions, systems, and thinking.
彼の判断は合理的だ。
His judgment is rational.
合理的な説明を求めている。
I'm looking for a rational explanation.
Emphasizes the use of reason and intellect, often contrasted with emotion or instinct. Slightly more formal or philosophical.
感情的にならず、理性的に話し合おう。
Let's discuss this rationally, without getting emotional.
Literally 'in accordance with reason'. A natural phrase meaning something is logical or makes sense.
彼の提案は理にかなっている。
His proposal is rational.
Describing a person, action, or choice that is based on good judgment and practicality.
Means having good sense or discretion. Often used for people who make sound, practical decisions.
彼は分別のある人だ。
He is a rational person.
Means wise or sensible. Often used for decisions or actions that are prudent and well-considered.
それは賢明な選択だ。
That's a rational choice.
Also works for practical, efficient choices, but leans more toward logical consistency.
Describing a person's mental state as calm, lucid, and capable of reasoning.
Means 'sane' or 'in one's right mind'. Used when contrasting with irrational or crazy behavior.
彼は正気とは思えない。
He doesn't seem rational.
Means calm and composed. Often implies the ability to think rationally under pressure.
冷静になって、理性的に考えて。
Calm down and think rationally.
Referring to numbers that can be expressed as a fraction.
The mathematical term for 'rational number'. Not used in everyday language.
有理数と無理数の違いを説明してください。
Please explain the difference between rational and irrational numbers.
The katakana word ラショナル is sometimes used in technical contexts (e.g., 'rational统一'), but it is not a natural way to express the general concept of 'rational' in Japanese. Stick to the native Japanese terms above.
合理的 (gōriteki) focuses on logical consistency and efficiency, often used for systems, plans, and decisions. 理性的 (riseiteki) emphasizes the use of reason and intellect, often in contrast to emotion. For 'rational thinking', both can work, but 合理的 is more common in everyday contexts.
合理的な判断を下した。
I made a rational decision.