Raisins are desiccated grapes; they're also dehydrated grapes. And yet, a close look at the etymologies of desiccate and dehydrate raises a tangly question. In Latin siccus means "dry," whereas the Greek stem hydr- means "water." So how could it be that desiccate and dehydrate are synonyms? The answer is in the multiple identities of the prefix de-. It may look like the same prefix, but the de- in desiccate means "completely, thoroughly," as in despoil ("to spoil utterly") or denude ("to strip completely bare"). The de- in dehydrate, on the other hand, means "remove," the same as it does in defoliate ("to strip of leaves") or in deice ("to rid of ice").