Cute Young Brunette Girl Practicing Yoga Poses

In Hindu philosophy, Yoga is the name of one of the six orthodox philosophical schools. The Yoga philosophical system is closely allied with the Samkhya school. The Yoga school as expounded by the sage Patanjali accepts the Samkhya psychology and metaphysics, but is more theistic than the Samkhya, as evidenced by the addition of a divine entity to the Samkhya's twenty-five elements of reality. The parallels between Yoga and Samkhya were so close that Max Müller says that "the two philosophies were in popular parlance distinguished from each other as Samkhya with and Samkhya without a Lord...." The intimate relationship between Samkhya and Yoga is explained by Heinrich Zimmer:
These two are regarded in India as twins, the two aspects of a single discipline. Sāṅkhya provides a basic theoretical exposition of human nature, enumerating and defining its elements, analyzing their manner of co-operation in a state of bondage ("bandha"), and describing their state of disentanglement or separation in release ("mokṣa"), while Yoga treats specifically of the dynamics of the process for the disentanglement, and outlines practical techniques for the gaining of release, or "isolation-integration" ("kaivalya").
Patanjali is widely regarded as the founder of the formal Yoga philosophy. Patanjali's yoga is known as Raja yoga, which is a system for control of the mind. Patanjali defines the word "yoga" in his second sutra, which is the definitional sutra for his entire work:
योग: चित्त-वृत्ति निरोध: