Catharsis (from Greek κάθαρσις katharsis meaning "purification '' or "cleansing '') is the purification and purgation of emotions -- particularly pity and fear -- through art or any extreme change in emotion that results in renewal and restoration. It is a metaphor originally used by Aristotle in the Poetics, comparing the effects of tragedy on the mind of a spectator to the effect of a cathartic on the body.
who said the function of tragedy is to produce the katharsis of pity and fear
Aristotle