Linked from
The 12 pages that link to Efflorescence, each with the reason it gives.
HydrateRelated: Some hydrates release water spontaneously when ambient humidity is low.
HydrationCompared with: Efflorescence releases water from hydrated solids instead of taking it up.
HygroscopyCompared with: It contrasts with moisture uptake by describing water loss from a solid.
Salt flatRelated: It forms when salts migrate upward and crystallize at the flat's surface.