Which term refers to the tool used for measuring humidity?

The term that refers to the tool used for measuring humidity is a hygrometer. Hygrometers are specifically designed to measure the amount of moisture or water vapor present in the air. These devices can operate on various principles, including the absorption of moisture by materials or the change in electrical resistance due to humidity levels.

The other terms relate to different measurements: a hypometer is not a widely recognized instrument in scientific contexts, a hydrometer is used for measuring the specific gravity of liquids, often by determining the density relative to water, and a thermometer is used to measure temperature. Understanding the distinct functions of these instruments clarifies why the hygrometer is the precise tool for measuring humidity.