The Sanskrit noun योग yoga is derived from the root yuj "to attach, join, harness, yoke". The word yoga is cognate with English "yoke".
The spiritual sense of the word yoga first arises in Epic Sanskrit, in the second half of the 1st millennium BCE, and is associated with the philosophical system presented in the Yoga Sutras of Patanjali, with the chief aim of "uniting" the human spirit with the Divine.
The term kriyāyoga has a technical meaning in the Yoga Sutras (2.1), designating the "practical" aspects of the philosophy, i.e. the "union with the supreme" due to performance of duties in everyday life.
According to Pāṇini, the term yoga can be derived from either of two roots, yujir yoga (to yoke) or yuj samādhau ("to concentrate"). In the context of the Yoga Sutras of Patanjali, the root yuj samādhau (to concentrate) is considered by traditional commentators as the correct etymology. In accordance with Pāṇini, Vyasa who wrote the first commentary on the Yoga Sutras, states that yoga means samādhi (concentration).
According to Dasgupta, the term yoga can be derived from either of two roots, yujir yoga ("to yoke") or yuj samādhau ("to concentrate"). Someone who practices yoga or follows the yoga philosophy with a high level of commitment is called a yogi (may be applied to a man or a woman) or yogini (a woman).