rational
adj.
late 14c., "pertaining to reason;" mid-15c., "endowed with reason," from Old French racionel and directly from Latin rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason" (see ratio).
〔李〕[rat;-ion;-ala.] a.有理性的； 有理的 n.有理数 ←rat (L reri,ratus)=to think or judge 想，判断