/ ˈræʃnəl; NAmE / adjective
1.
( of behaviour, ideas, etc. ) based on reason rather than emotions :
a rational argument / choice / decision
rational analysis / thought
There is no rational explanation for his actions.
2.
( of a person ) able to think clearly and make decisions based on reason rather than emotions
SYN reasonable :
No rational person would ever behave like that.
OPP irrational
► ra·tion·al·ity / ˌræʃəˈnæləti; NAmE / noun [ U ]:
the rationality of his argument
► ra·tion·al·ly / ˈræʃnəli; NAmE / adverb :
to act / behave / think rationally
She argued her case calmly and rationally.
••
WORD ORIGIN
late Middle English (in the sense having the ability to reason ): from Latin rationalis , from ratio(n-) reckoning, reason, from rat- reckoned, from the verb reri .