Yoga is not worship; nor is it a sacrifice to propitiate a Deity. The word yoga comes from the root 'yug' which means to join. It is described in the Vishnu Purana as follows:

"Having controlled all senses with the mind, the idea of unity of the self, with the supreme self within, is yoga."

According to Bhagavath Githa, yoga is the mind getting merged with the soul within, freeing itself from all attachments that bring about pain. The yoga sutra says that it is restraint of mental modifications or control of thought waves in mind.

"Yogaschittavrithi Nirodha"

Mrs. Annie Besant says that it is a science by which alone spiritual truths can be fully realised by the gradual unfolding of the inner faculties, which enable man to study the invisible world directly by the expansion of his consciousness to embrace wider and subtler ranges of being.

The object of yoga is to get moksha, that is to say, to emancipate the individual self from its bondage to the material world by a process of mental and bodily discipline culminating in a spiritual transformation and merger of the self with the supreme self, the God within. This merger secures for the yogi the moksha which is freedom from re-birth the bugbear of all thinking Hindus and others who believe in re-birth.

Yoga is said to be a prevedic cult. This was systematised on a scientific basis by sage Kapila who lived about the 7th century B.C. This organised wisdom which influenced the buddhist thought a good deal came to be known as sankya yoga or sankya philosophy. About five centuries later sage Pathanjali popularised it by introducing certain steps-in-aid known as Ashtanga (eight limbs of aid.) He also insisted that a fervent devotion to God should also be considered as an indispensable factor in the practice of yoga, although five centuries before him, Sage Kapila did not think so.