What does a thermometer measure?

A thermometer measures temperature, which is the degree of warmth or coldness of an object or environment. It works on the principle that substances expand or contract with temperature changes; for example, in a mercury or alcohol thermometer, the liquid inside expands when heated and rises in a calibrated scale to indicate the temperature. This makes thermometers reliable instruments for a variety of applications, from weather monitoring to laboratory experiments and medical uses.

The other choices refer to different measurements: pressure gauges measure atmospheric pressure, hygrometers assess humidity levels, and anemometers are used to determine wind speed. Each of these instruments has its own specific function and is designed to measure different physical properties, making them unsuitable for measuring temperature.