Prana (Devanagari: prána) is a Sanskrit word meaning 'breath' and is understood as the vital, life-sustaining force of living beings and the vital energy in all natural processes of the universe. It is a central concept in Eastern medicine and Yoga where it is understood to flow through a network of fine subtle channels called nadi. The three main channels are: the ida, the pingala, and the sushumna. The ida and pingala channels are said to correlate with left and right uninostril breathing. If Prana enters a period of uplifted, intensified activity, the Yogic tradition refers to this stage of Prana as Pranotthana. Its first expounding came in the Upanishads, where it is part of the worldly, physical realm, sustaining the body and the mother of thought and thus also of the mind. Prana suffuses all living form. The Jeeva, the animal soul is the form it takes on by doing so.