1. an instrument that indicates changes in atmospheric humidity without measuring the exact amount of moisture
Usage: scientific instrument; less common than hygrometer

Examples

• The hygroscope on the wall showed that humidity levels were rising.
• Unlike a hygrometer, a hygroscope only indicates whether the air is becoming more or less moist.
• The scientist used a hygroscope to monitor relative humidity changes in the laboratory.
• A simple hygroscope can be made from materials like human hair or wood that respond to moisture.
• The hygroscope's needle moved as the atmospheric conditions changed throughout the day.