able to reason 能推理的: Man is a rational being. 人是有理性的生物. 
not foolish or absurd; sensible; reasonable 出於理性的; 理智的; 明事理的; 讲道理的: rational conduct 合理的行为 * a rational argument, explanation, solution, etc 合乎情理的论证﹑ 解释﹑ 解决方法等. 
lucid or sane 头脑清醒的; 神志正常的: Despite her recent stroke, she is quite rational. 她尽管最近曾患中风, 但头脑仍很清醒. * No rational person would go to work in his pyjamas. 任何神志正常的人都不会穿着睡衣去上班.> rationality / 9rAFE5nAlEtI; 9rAFE`nAlEtI/ n [U] quality of being rational; reasonableness 理性; 合理性; 理智; 推理能力.
rationally / -FnElI; -FEnlI/ adv: think, behave, argue rationally 思考﹑ 行为﹑ 辩论合情合理.