The device used to measure humidity is called a hygrometer. Hygrometers come in various types, including analog and digital versions, and they work by measuring the amount of moisture in the air. Some common types include psychrometers, which measure humidity using the principles of evaporation, and electronic hygrometers, which use sensors to detect humidity levels. Humidity is an important factor in weather forecasting, climate studies, and even in everyday situations, such as maintaining indoor comfort levels and ensuring proper conditions for certain industries, like agriculture and food storage.