A chemical compound containing water molecules in a proportion equal to half the number of molecules of the main substance.
From 'hemi-' (half) + 'hydrate' (compound with water), formed in chemistry to describe crystalline solids containing a specific ratio of water—the most famous being gypsum hemihydrate.
Plaster of Paris is actually a hemihydrate—it's made by heating gypsum and removing some water, and when you add water back, it hardens into a solid! This half-water compound is why plaster has been used for art and construction for thousands of years.
Complete word intelligence in one call. Free tier — 50 lookups/day.