What does hygroscopic mean?
Hygroscopic describes a substance or material that attracts moisture from the air. Such materials may absorb water vapour and swell, dissolve, or form a damp layer, depending on the substance and the surrounding humidity. The term is especially common in chemistry, materials science, pharmaceuticals, and food technology, where moisture uptake can affect stability, storage, and handling. Hygroscopic behaviour is familiar in everyday materials such as table salt, sugar, and some powdered chemicals. It is distinct from being merely absorbent, since hygroscopicity specifically involves taking up moisture from the surrounding atmosphere. The word is also useful in technical discussions of humidity sensors, desiccants, packaging, and products that need protection from environmental moisture.
adjectiveHygroscopic means tending to attract moisture from the surrounding air. In science and engineering, it describes materials that absorb water vapour, sometimes to the point of dissolving in it.
- Tending to attract or absorb moisture from the surrounding air.
"The salt is hygroscopic, so it must be stored in a sealed container."
"The powder is highly hygroscopic and should be kept in an airtight container."
"Hygroscopic materials are important in humidity sensors and moisture-control systems."
Hygroscopic materials quietly pull water from the air, which is why familiar substances such as table salt and sugar can become damp or clump when exposed to humidity.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does hygroscopic come from?
The word comes from Greek hygros, meaning “wet” or “moist,” and skopein, meaning “to look at” or “examine.” The related English word hygroscope refers to an instrument for measuring atmospheric humidity. The combining form hygro- was adopted into scientific vocabulary, giving rise to terms such as hygrometry, the measurement of moisture.
Related word forms
How hygroscopic is actually used
This is primarily a technical term used in chemistry, materials science, pharmaceuticals, and food technology. It is more precise than simply saying that something is damp or absorbent, because the moisture is drawn from the atmosphere.
Easily confused with hygroscopic
A hygroscopic material attracts moisture from the air, whereas a hydrophilic material has an affinity for water and is readily wetted by it.
Deliquescent describes a substance that absorbs enough atmospheric moisture to dissolve in the water it takes up; hygroscopic describes the broader tendency to attract moisture.