Vṛtti

Fluctuations or modifications of the mind. These are the constant movements of citta that create the ordinary experience of the world. In YS 1.2, yoga is the restriction of the vṛttis: yogaḥ citta-vṛtti-nirodhaḥ.

Patañjali identifies five types of vṛttis: pramāṇa (valid cognition), viparyaya (error), vikalpa (verbal concept), nidrā (sleep), and smṛti (memory). Each can be painful (kliṣṭa) or non-painful (akliṣṭa).

Yoga doesn’t seek to eliminate vṛttis — they’re a natural part of mental functioning — but to develop the capacity to still them at will (nirodha), allowing consciousness to remain in its own nature. Their stillness is the very essence of yoga.