Definition of "sane"

sane

/seɪn/

adjective
comparative saner, superlative sanest
1. Being in a healthy condition; not deranged; thinking rationally.
2. Mentally sound; possessing a rational mind; having the mental faculties in such condition as to be able to anticipate and judge the effect of one's actions in an ordinary manner.
  Quotations
  Shepard: What's wrong with your assistant?Dr. Warren: Manuel has a brilliant mind, but he's always been a bit... unstable. Genius and madness are two sides of the same coin.Dr. Manuel: Is it madness to see the future? To see the destruction rushing towards us? To understand there is no escape? No hope? No, I am not mad. I'm the only sane one left!Dr. Warren: I gave him an extra dose of his meds after the attack.
  2008, BioWare, Mass Effect (Science Fiction), Redwood City: Electronic Arts, PC, scene: Eden Prime
3. Rational; reasonable; sensible.