Herbology is the therapeutic use of herbs in treatments and diet. In the United States, herbal medicine generally refers to a system of medicine that uses European or North American plants. Traditional Chinese medicine (TCM) uses plants native to China or Asia, while Ayurvedic herbal medicine uses plants native to India. Modern herbalists often use plants from many different regions of the world, and they do not restrict their practice only to those plants classified as an herb (a seed plant whose stem withers away annually). Instead, in medicine, an herb can be a root, a piece of tree bark, a mushroom, or anything else which falls into the plant kingdom