The Four Energies
The energies of herbs are classified as cold, hot, warm, or cool, based on their observed effects in ancient Chinese applications. An herb that effectively treats a hot syndrome is considered to have a cold energy, while one that treats a cold syndrome is considered to have a hot energy. These energies are categorized broadly into yin and yang, with cold and cool energies belonging to yin, and hot and warm energies belonging to yang. To express subtle temperature differences, Chinese physicians use phrases such as 'extremely warm' or 'slightly cold'.