The major premise of Chinese medical theory is that all the forms of life in the universe are animated by an essential life-force or vital energy called qi (氣). 氣 also means "breath" and "air" in Chinese, and is similar to the Hindu practice of prana. 氣 is often understood as transferable and transmutable: digestion extracts 氣 from food and drink and transfers it to the body; breathing extracts 氣 from air and transfers it to the lungs. When these two forms of 氣 meet in the blood stream, they transmute to form human-氣, which then circulates throughout the body as vital energy. It is the quality, quantity, and balance of your qi that determines your state of health and span of life.