The instrument used to measure humidity is called a hygrometer. Hygrometers are essential tools in meteorology, agriculture, and various industrial applications, as they help monitor and maintain optimal humidity levels. There are several types of hygrometers, including mechanical, electronic, and digital models. Mechanical hygrometers typically use materials that change in size or shape with moisture levels, while electronic versions use sensors to provide precise humidity readings. Accurate humidity measurement is important for weather forecasting, controlling indoor environments, and ensuring the proper storage of perishable goods, as high or low humidity can significantly impact various processes.