What is hydroscopicity?

Answer 1

Many materials, such as that of timber and wood, are extremely susceptible to swelling and shrinking caused by the absorption of water from changing relative humidity in the atmosphere. In this sense, hydroscopicity is the measure of a wood's ability to absorb moisture, causing an increase in wood volume and mass.

Hydroscopicity can also be used to describe the behaviour of water with other materials; in reverse osmosis membrane technology, membranes are deemed 'hydroscopic' if they allow water to flow on their surface more freely. The opposite of this is 'hydrophobic' membranes, which resist water flow more notably.