The Yoga Sutras of Patanjali is a Hindu scripture and foundational text of Yoga. It forms part of the corpus of Sutra literature dating to India’s Mauryan period. In Hindu philosophy, Yoga (also Raja Yoga to distinguish it from later schools) is the name of one of the six orthodox philosophical schools. Though brief, the Yoga Sutras are an enormously influential work on yoga philosophy and practice.
Definition courtesy Wikipedia.