How to say "rational" in Japanese

• 合理的ごうりてきCommon
  na-adjectiveCovers rational in the sense of logical and reasonable: choices, arguments, or plans based on sound reasoning. Typical when discussing decisions, explanations, and ways of thinking.
  彼女かのじょの思考法しこうほうは合理的ごうりてきだった。↗

  Her way of thinking was rational.
• 理性的りせいてきCommon
  na-adjectiveCovers rational as governed by reason rather than emotion: a calm, level-headed person or reaction. Used when contrasting sensible behavior with acting on feeling.
  あなたはもっと理性的りせいてきであるべきだ。↗

  You should be more reasonable.

Use 合理的 for rational in the sense of logical, sensible, or efficient reasoning and choices, and 理性的 for rational as in governed by reason rather than emotion, describing calm, level-headed people or behavior.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 合理的ごうりてきrational
• 理性的りせいてきrational
• 有理ゆうりrational
• ラショナルrational
• 筋の通ったすじのとおったrational