A commonly used tool defined as a device to measure temperature is a thermometer. Thermometers are essential instruments in various fields, including medicine, science, and meteorology. They operate by measuring the expansion or contraction of a liquid (typically mercury or alcohol) or through the electronic sensing of temperature changes. In medicine, thermometers are often used to check body temperatures to detect fever and other health conditions. Modern digital thermometers provide quick and accurate readings, while traditional glass thermometers offer a more classic approach. Understanding temperature is crucial for numerous applications, from cooking to scientific experiments.