ratio-, reason-

(Latin: reckoning, to reckon; calculating, calculation; understanding; thinking)

unreasonable (adjective), more unreasonable, most unreasonable
1. Unable to act according to good judgment; irrational: It seems to be a very unreasonable idea to have a picnic in the rain and get completely wet!
2. Beyond moderation: The payment Tom got was much too little for the very hard labor he had to do, so it was totally unreasonable and he complained to his boss.
unreasonably (adverb), more unreasonably, most unreasonably
1.Concerning how something surpasses the limits of moderation or reason: Tom told his mother after coming home from school that the German test was unreasonably and extremely difficult and that he probably failed.
2. Descriptive of how a person acts in an unintelligent or irrational manner: Jack behaved in an unreasonably crazy way after hearing that his wife wanted a divorce.