reasonable vs. rational
 

I had a students ask me what the difference in meaning and usage is between reasonable and rational.

I was pretty stumped but answered 'reasonable' is a feeling or emotion where 'rational' is based on logic.

What do you think?

Re: reasonable vs. rational
 

Yes - rational certainly means based on logic rather than emotion, Star Trek's Vulcans being the best example. If you can deduce something from evidence, then it's rational.

Reasonable does let in emotion though. If you say It's not reasonable to expect a teacher to teach forty hours a week there's the feeling of "Oh poor thing" as well as logical reasons like because she won't do the thing well. It conveys the idea of "fair and sensible" rather than just "logical".

But it can also mean "acceptable but not very good" A reasonable number of students passed the exam / They have quite reasonable prices.

Re: reasonable vs. rational
 

I agree that rational is 'coldly logical' and 'reasonable' is a feeling. I tell my reasonable is close to 'understandable.' If a restaurant has reasonable prices, then they aren't high or low--they're 'understandable,' considering the quality and portions of the food you get.

If a person is behaving 'reasonably,' it means you can understand why they're behaving the way they are.