Learner's definition of SANE
[also more sane; most sane]
1 : having a healthy mind : able to think normally
He is perfectly sane. [=he is not mentally ill]
No sane person could do something so horrible.
Trips to the beach keep me sane. [=keep me feeling happy and able to deal with life without becoming too upset, nervous, etc.]
It's hard to stay/remain sane [=to stay relaxed, calm, etc.] when I'm so busy.
2 : based on reason or good judgment : rational or sensible