Unani medicine, also called Unani tibb, Arabian medicine, or Islamic medicine, a traditional system of healing and health maintenance observed in South Asia. The origins of Unani medicine are found in the doctrines of the ancient Greek physicians Hippocrates and Galen. As a field, it was later developed and refined through systematic experiment by the Arabs, most prominently by Muslim scholar-physician Avicenna. During the Caliphate (the political-religious Muslim state that began in 632 CE), the bulk of Greek knowledge was translated into Arabic, part of that knowledge being the principles of medicine. With additional contributions of medical wisdom from other parts of the Middle East and South Asia, Unani medicine came to be known also as Arabian, or Islamic, medicine.