The instrument often used to measure temperature is called a thermometer. Thermometers come in various types, including digital, mercury, and infrared, each suited for different applications. A traditional mercury thermometer consists of a glass tube filled with mercury that expands or contracts in response to temperature changes, indicating the temperature on a calibrated scale. Digital thermometers use electronic sensors to provide a digital readout of temperature and are commonly employed in medical, industrial, and environmental contexts. Accurate temperature measurement is essential in numerous fields, including meteorology, medicine, and food safety, highlighting the thermometer's importance in everyday life.