What does a barometer measure?

A barometer is an instrument specifically designed to measure atmospheric pressure. It operates on the principle that changes in the weight of the air above us can affect weather patterns and altitude readings. When air pressure increases, it often indicates fair weather, while decreasing pressure can signal stormy conditions.

The other options relate to different meteorological measurements. Temperature is measured by a thermometer, humidity levels are gauged with a hygrometer, and wind speed is captured by an anemometer. Each of these instruments has a dedicated purpose, unlike the barometer, which focuses solely on air pressure. Thus, the correctness of the answer lies in the specific function of the barometer in measuring atmospheric pressure.