rational


rational
adjective
1 based on clear, practical or scientific reasons: It can't have just disappeared! There must be a perfectly rational explanation.
2 sensible and able to make decisions based on intelligent thinking rather than on emotion: rational behaviour | We should be able to sort this out like rational human beings!
— rationally adverb: Scientific training makes you think rationally. — rationality noun (U) —opposite irrational

Longman dictionary of contemporary English. 2004.

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