rational 
英 [ˈræʃənəl]  美 [ˈræʃnəl] 
adj. 理性的；明事理的；合理的

例句：
Look at both sides of the case and come to a rational decision. 

看看问题的正反两面，再理性决策。

the power of rational thought 

理性思维的力量

Rachel looked calmer and more rational now. 

这会儿雷切尔似乎平静一些，也理智一些了。

The voice sounded perfectly rational but what it was saying was completely mad. 

听声音倒是再清醒不过，说的内容却全是胡言乱语。