Yoga (from the Sanskrit root yuj ("to yoke")) refers to a series of interrelated ancient Hindu spiritual practices that originated in India, where it remains a vibrant living tradition. Yoga is one of the six orthodox systems (darshans) of Indian philosophy. Its influence has been widespread among many other schools of Indian thought. In Hinduism, Yoga is seen as a system of self-realization and a means to enlightenment. It is also a central concept in Buddhism, Sikhism, Jainism and has influenced other religious and spiritual practices throughout the world. The basic text of Yoga, the Yoga-sutras, is attributed to Patañjali, who lived in India around 150 B.C.E.During the twentieth century, the philosophy and practice of Yoga became increasingly popular in the West. The Yoga taught in the West as a form of physical fitness, weight control, and self-development is commonly associated with the asanas (postures) of Hatha Yoga; the deeper philosophical aspects of yoga are often ignored.