The word "Yoga" in Samskrit, is derived from the root "Yuj", meaning "to unite", "yoking". The usage of this word Yoga differs from one Science to another, some of which are
- In Yoga Sutra, Yoga is the union of humans and the cosmos, the union of Microcosm and the Macrocosm
- In Jyotisha Shastra or Indian Astrology, it is the union of two planets in a house in the Horoscope like Gajakesari Yoga
- In Ayurveda, Yoga is used to describe a medicinal preparation like Visha Yoga (antidote preparation) or a compilation of medicinal preparations like Yoga Ratnaakara, Sahasra Yogam(both are books containing a variety of medicinal preparations)
- In Vedanta, Yoga is the union of Jeevaatman (individual soul) with Paramaatman (Supreme soul or Supreme Being) in Visishtaadvaita ('qualified nondualism' where God, as Ishwara, is the third reality in this inseparable trinity). In Advaita, Yoga is the realization of the oneness of Jeevaatman and Paramaatman.
Yoga Sastra or Yoga is among the six Darsanas or the six schools of Indian philosophy. The Aim of Yoga is the attainment of Moksha or Salvation. To attain this state of ultimate bliss, Yoga describes an eight-fold path called "Ashtaanga Yoga".