A clinical thermometer, often referred to as a mercury thermometer, is a traditional medical device used to measure a person's body temperature. It consists of a narrow glass tube with a bulb at one end and a reservoir containing mercury (a silver-colored liquid metal) at the other end. Due to the health and environmental risks associated with mercury, many countries have phased out the use of mercury thermometers in favor of safer alternatives, such as digital thermometers. Digital thermometers use electronic sensors to measure temperature and provide rapid and accurate readings without the risk of mercury exposure.