http://www.swamij.com/yoga-sutras-10104.htm#1.2
1.2 Yoga is the control (nirodhah, regulation, channeling, mastery, integration, coordination, stilling, quieting, setting aside) of the modifications (gross and subtle thought patterns) of the mind field.(yogash chitta vritti nirodhah)
yoga = of yoga, union; literally, to yoke, from the root yuj, which means to join; same as the absorption in samadhi
chitta = of the consciousness of the mind-field
vritti = operations, activities, fluctuations, modifications, changes, or various forms of the mind-field
nirodhah = control, regulation, channeling, mastery, integration, coordination, understanding, stilling, quieting, setting aside of
