理性|りせいrisei[1]atamadaka (head-high)

1. nounreason; reasoning power; (one's) sense
   人間にんげんには理性りせいがあるが動物どうぶつには無ない。↗

   Man has reason, animals do not.

• Related知性ちせいNeutralIntelligence for understanding and judging things, suggesting a cultured, sharp mind, as in 「知性あふれる人」. 「理性」 stresses holding emotion in check and acting by reason.
• Related理知りちWrittenWritten/formal prose: calm thinking and judgment based on reason and knowledge, often as 「理知的」. 「理性」 is more often set against emotion, as in 「理性を失う」.
• Antonym感情かんじょうNeutralEmotions such as joy, anger, sorrow and pleasure, the opposite of the calm thinking of 「理性」; the pair 「理性と感情」 is common.
• Antonym本能ほんのうNeutralInborn impulses and desires that drive behavior; opposed to the conscious reasoning of 「理性」.

Use 「理性」 for thinking and acting by reason, keeping emotion in check. 「知性」 suggests cultivated intelligence; 「理知」 is the written/formal word for calm, reasoned judgment. 「感情」 and 「本能」 are the opposites: emotion and instinct.

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

1. 筋道すじみちを立たてて物事ものごとを考かんがえる能力のうりょく。