2. Regarding to a person who is sane, lucid, and able to make sound judgments: The doctor indicated that the patient was rational and should not be detained in the hospital.
3. Descriptive of something a person clarifies which is sensible and reasonable and not emotional: Jason's explanation for being late seemed rational to him but not to his parents.
Jeff's friend elucidated the rationale behind his early retirement, but Jill still didn't comprehend the rationale for his decision.
The rationale that Kristie's normally rational friend gave her for getting her speeding ticket was unbelievable.
Mark explained to his wife the rationale of why he was retiring early from his career as a writer of novels.2. Etymology: from Latin rationalis, "of or belonging to reason."