Yoga
Yoga (Sanskrit, "union") is an ancient Hindu philosophical-spiritual system, codified by Patanjali in the Yoga Sutras (c. 2nd century BC-4th century AD). Includes eight limbs (Ashtanga): yama (ethics), niyama (discipline), asana (postures), pranayama (breath), pratyahara (introspection), dharana (concentration), dhyana (meditation), samadhi (absorption).
Modern Western yoga
Modern yoga in the West (Hatha Yoga, Ashtanga of Pattabhi Jois, Iyengar, Bikram, Vinyasa) emphasizes the third limb (asanas — postures). The complete system involves the eight limbs, mostly ignored in commercial fitness yoga.