The common instrument used to measure temperature is the thermometer. Thermometers can be found in various forms, including digital, mercury, and alcohol types. They measure temperature based on physical or electrical phenomena that change with temperature variations. In a traditional mercury thermometer, mercury expands and rises in a calibrated glass tube as the temperature increases. Digital thermometers, on the other hand, use electronic sensors to provide a quick and accurate reading. Thermometers are essential tools in numerous settings, including medical, meteorological, culinary, and industrial applications.