Diagnosis
Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines with variations in the use of logic, analytics, and experience to determine "cause and effect". In systems engineering and computer science, it is typically used to determine the causes of symptoms, mitigations, and solutions.
Therapy
Therapy (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a diagnosis. In the medical field, it is usually synonymous with treatment (also abbreviated tx or Tx). Among psychologists and other mental health professionals, including psychiatrists, psychiatric nurse practitioners, counselors, and clinical social workers, the term may refer specifically to psychotherapy (sometimes dubbed 'talking therapy'). The English word therapy comes via Latin therapīa from Greek: θεραπεία and literally means "curing" or "healing".
Therapy
I used to be under the impression that in some kind of wanky, bullshit way, acting was like therapy: you get in and grapple with and exorcise all those demons inside of you. I don't believe that anymore. It's like a snow shaker. You shake the thing up, but it can't escape the glass. It can't get out. And it will settle until the next time you shake it up.
Gary Oldman in Henri Béhar "Gary Oldman on "Nil by Mouth" at filmscouts.com, 1997.05.08: Film Scouts Interview