Describes a person, attitude, or decision based on reason rather than emotion. Often used in contrast with 感情的 (emotional).
彼はいつも理性的な判断をする。
He always makes rational decisions.
感情的にならず、理性的に話し合おう。
Let's discuss this rationally, without getting emotional.
理性的 describes a calm, reason-guided attitude or person, whereas 論理的 describes the logical coherence of an argument or thought process itself.
理性的 describes a person's calm, reason-driven character or state of mind, whereas 合理的 typically describes decisions, systems, or explanations.
理性的 describes acting on reason and logic, directly opposed to 感情的 behavior driven by feelings.
Compound of 理性 (reason) + 的 (-like, -ical). 理性 is from Chinese 理性 (lǐxìng), and 的 is a Sino-Japanese suffix forming adjectival nouns.