an instrument that indicates the approximate humidity of the air.

What does the term hygroscopic means?

1 : readily taking up and retaining moisture hygroscopic soils. 2 : taken up and retained under some conditions of humidity and temperature hygroscopic water in clay.

What is the difference between hygroscopic and Hydroscopic?

Simply stated, hygroscopic materials absorb moisture, whereas hydrophobic materials do not absorb moisture from the environment.