What does hydrous mean?
Hydrous is a technical adjective meaning that a substance contains water. In chemistry, it distinguishes substances in which water is present, or chemically bound, from anhydrous substances, which contain no water. The term is especially useful when describing mineral and crystal forms whose properties can change depending on whether water is included in their structure. For example, a hydrous salt may lose water on heating and become an anhydrous compound. Although the basic idea of hydrous is straightforward, the word is most useful in scientific and industrial contexts rather than ordinary conversation.
adjectiveContaining water or water in chemical combination. In chemistry, a hydrous substance contains water as part of its molecular or crystal structure, as opposed to being anhydrous.
- Containing water, especially as a constituent of a chemical substance.
"The hydrous form of the compound loses water when it is heated."
"Hydrous minerals often undergo a visible change when they are heated."
"The sample was stored in a hydrous form to prevent it from drying out."
Hydrous is the chemical opposite of anhydrous: one contains water, while the other contains none.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does hydrous come from?
Hydrous was formed in the 19th century from the Greek hydor, meaning “water,” combined with the suffix -ous. It belongs to a family of English words built on the same root, including hydrate, hydration, hydrogen, and hydrocarbon. In its chemical sense, it developed as the counterpart of anhydrous, describing a substance that contains water rather than one that does not.
Related word forms
How hydrous is actually used
This is primarily a technical term used in chemistry, mineralogy, and related sciences. It is more precise than simply saying that something is wet, because it can refer to water chemically bound within a substance.
Easily confused with hydrous
A hydrous substance contains water, whereas an anhydrous substance contains no water, including no chemically bound water.
Humid describes air that contains water vapour, while hydrous describes a substance that contains water or is chemically combined with it.