Containing no water or very little water; describes a chemical compound or substance from which water has been removed.
From Greek an- (without) + hydro (water) + -ous (adjective suffix). This term became standard in chemistry in the 1800s to distinguish between compounds with and without water molecules attached.
Anhydrous calcium chloride is so eager to grab water that it gets hot enough to burn skin—it's used in labs precisely because its hunger for water makes it incredibly reactive and useful.
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