Ashtanga yoga: अष्टाङ्गयोग: aṣṭāṅgayoga, “the eight limbs of yoga”) is Patanjali’s classification of classical YOG, as set out in his Yog Sutras. He defined the eight limbs as Yamas (abstinences), Niyama (observances), Asana (postures), Pranayama (breathing), Pratayahara (withdrawal), Dharama (concentration), Dhyana (meditation) and Samadhi (absorption).
The eight limbs form a sequence from the outer to the inner. Postures, important in modern yoga as exercise, form just one limb of Patanjali’s scheme; he states only that they must be steady and comfortable. The main aim is kaivalya, discernment of Purusha, the witness-conscious, as separate from Prakirti, the cognitive apparatus, and disentanglement of Purusha from its muddled defilements.