Longman Dictionary of Contemporary English homepage

Date: 1300-1400
Language: Latin
Origin: rationalis, from ratio; RATIO

rational

adjective
     
ra‧tion‧al
1 rational thoughts, decisions etc are based on reasons rather than emotions [≠ irrational]:
Parents need to be fully informed so they can make a rational decision.
I'm sure there's a rational explanation for all this.
It's impossible to have a rational conversation with him.
2 a rational person is able to think calmly and sensibly [≠ irrational]:
Culley was quite rational at the time of her baby's death.
3 formal able to make sensible judgments:
Man is a rational animal.
rationally adverb:
We were too shocked to think rationally.
rationality noun [uncountable]

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