This is the yoga sutra that defines yoga:
(Yoga is to allow the patterning of consciousness to subside and become still.)
yoga = union
citta = mind-stuff; consciousness; all that is perceived, however gross or subtle
vrtti = the form of the movement of this citta, that is like a vortex or whirlpool due to the dynamic of attraction to the desirable and the repulsion of the undesirable (I want this; I don’t want that). This drawing towards and pushing away creates a spin in consciousness: the vritti. It is often equated with the English word ‘modifications’. The English words ‘patterning’ and ‘turnings’ also give a good picture.
nirodha = stilling, cessation, restriction, not moving, subsiding
So this sutra points to yoga as the state of wholeness or union which becomes apparent when no longer covered over by the incessant movement of consciousness being stirred up by the spinning dynamic of attraction and repulsion. Consciousness then comes to rest on its own. It is then realized to be our natural state that already is now and eternally is.