noun
hygroscope
A physics instrument that indicates humidity changes, often using a material that expands or contracts with moisture.
検湿器は湿度の変化を視覚的に示す装置です。
A hygroscope is a device that visually indicates changes in humidity.
Compound of 検 (inspect) + 湿 (moisture) + 器 (instrument). A modern technical coinage; the exact derivation is uncertain.