Reason or rationality — the mental faculty for logical, calm judgment as opposed to emotion.
感情に流されず、理性で判断することが大切だ。
It's important to judge with reason rather than be swept away by emotion.
理性と感情のバランスを保つのは難しい。
Maintaining a balance between reason and emotion is difficult.
彼女は理性に基づいて冷静に話した。
She spoke calmly based on reason.