What is commonly used to measure temperature?

A thermometer is commonly used to measure temperature due to its ability to indicate the warmth or coldness of an object or environment. It operates based on the physical property that most substances expand when heated and contract when cooled. A typical thermometer contains a liquid, such as mercury or alcohol, in a glass tube. As the temperature rises, the liquid expands and rises in the tube; conversely, when the temperature falls, the liquid contracts and lowers down the tube. This property makes thermometers accurate and reliable tools for measuring temperature in various settings, from simple weather measurements to more complex laboratory applications.

Other options serve different functions: a barometer measures atmospheric pressure, a hygrometer measures humidity, and a calorimeter measures heat change in chemical reactions or physical processes. Therefore, these instruments are not designed to gauge temperature directly like a thermometer does.