The Sanskrit word yoga has many meanings, and is derived from the Sanskrit root "yuj", meaning "to control", "to yoke" or "to unite". Translations include "joining", "uniting", "union", "conjunction", and "means". It is also possible that the word yoga derives from "yujir samadhau," which means "contemplation" or "absorption." This translation fits better with the dualist Raja Yoga because it is through contemplation that discrimination between prakrti (nature) and purusha (pure consciousness) occurs. As a term for a system of abstract meditation or mental abstraction it was introduced by Patanjali in the 2nd century BC. Someone who practices yoga or follows the yoga philosophy with a high level of commitment is called a yogi or yogini.

The goals of yoga are varied and range from improving health to achieving moksha. Within the Hindu monist schools of Advaita Vedanta, Shaivism and Jainism, the goal of yoga takes the form of moksha, which is liberation from all worldly suffering and the cycle of birth and death (samsara), at which point there is a realization of identity with the Supreme Brahman. In the Mahabharata, the goal of yoga is variously described as entering the world of Brahma, as Brahman, or as perceiving the Brahman or Atman that pervades all things. For the bhakti schools of Vaishnavism, bhakti or service to Svayam Bhagavan itself may be the ultimate goal of the yoga process, where the goal is to enjoy an eternal relationship with Vishnu.

The Sanskrit word yoga has the meaning of union. A serious practitioner of Yoga (someone pursuing the higher spiritual and religious goals of Yoga) takes upon themselves a life of austere self-discipline common to nearly all forms of mystical and religious life. The practices that constitute this self-disciplined life are called in yoga yama and niyama. This self-discipline is the 'yoke' that one puts upon oneself for the purpose of attaining moksha. An alternative definition is that Yoga is the method of yoking, or unifying, the "lower" (egoistic) personality (those inclinations that in Hellenistic philosophy and Christianity are called passions) to the "higher" via a process of sublimation. In Vedic Sanskrit, the term "yoga" besides its literal meaning, the yoking or harnessing of oxen or horses, already has a figurative sense, where it takes the general meaning of "employment, use, application, performance" (compare the figurative uses of "to harness" as in "to put something to some use"). All further developments of the sense of this word are post-Vedic. A sense of "exertion, endeavour, zeal, diligence" is found in Epic Sanskrit. The more technical sense of the term "yoga", describing a system of meditation or contemplation with the aim of the cessation of mental activity and the attaining of a "supreme state" arises with early Buddhism (5th century BC), and is adopted in Vedanta philosophy by the 4th century BC.

Outside India, the term yoga is typically associated with Hatha Yoga and its asanas (postures) or as a form of exercise. Someone who practices yoga or follows the yoga philosophy to a high level of attainment is called a yogi or yogini.