A hygrometer is the instrument used to measure humidity. It can be either analog or digital and operates by using various methods to detect moisture levels in the air. Some hygrometers use materials that change properties in response to humidity, while others rely on electrical sensors. Accurate humidity measurement is essential in various fields, including meteorology, agriculture, and HVAC (heating, ventilation, and air conditioning) systems, as humidity affects comfort levels, crop growth, and weather predictions.