Yoga is a group of physical, mental, and spiritual practices or disciplines that originated in ancient India. Yoga is one of the six orthodox philosophical schools of Hinduism.The International Day of Yoga has been celebrated annually on 21 June since 2015, following its inception in the United Nations General Assembly in 2014.The Indian Prime Minister, Narendra Modi, in his UN address in 2014, had suggested the date of 21st June, as it is the longest day of the year in the Northern Hemisphere and shares a special significance in many parts of the world.The posture of yoga is known as asan.The traditional number of asanas is the symbolic 84, but different texts identify different selections, sometimes listing their names without describing them.Some names have been given to different asanas over the centuries, and some asanas have been known by a variety of names, making tracing and the assignment of dates difficult.For example, the name Muktasana is now given to a variant of Siddhasana with one foot in front of the other, but has also been used for Siddhasana and other cross-legged meditation poses.As another example, the headstand is now known by the 20th century name Shirshasana, but an older name for the pose is Kapalasana. Sometimes, the names have the same meaning, as with Bidalasana and Marjariasana, both meaning Cat Pose.