“!!चित्त वृत्ति निरोध!!”
Saint Patanjali defined purpose of Yoga as चित्त वृत्ति निरोध, as second aphorism in first chapter of his book Yoga Sutras.
This is beautifully translated by BKS Iyenger as ‘the restraints(निरोध) of mental(चित्त) modifications (वृत्ति) or as suppression(निरोध) of the fluctuations(वृत्ति) of consciousness (चित्त)’