To gradually melt or dissolve by absorbing moisture from the air and becoming liquid.
From Latin 'deliquescere' (de- 'completely' + liquescere 'to become liquid'), which itself comes from 'liquere' (to be liquid). The '-esce' suffix indicates a process of becoming or changing state.
Calcium chloride and some sodium salts actually deliquesce in humid air—they literally turn into liquid puddles!—which is why weather scientists study these substances to understand atmospheric moisture.
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