De- : A prefix from Latin de down, from, away; as in debark, decline, decease, deduct, decamp. In words from the French it is equivalent to Latin dis-apart, away; or sometimes to de. Cf. Dis-. It is negative and opposite in derange, deform, destroy, etc. It is intensive in deprave, despoil, declare, desolate, etc.

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How to locate Rio de Janeiro city in Gondwana ?

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Defination from the web:
DE. Differential equation, in mathematics, an equation in which the derivatives of a function appear as variables ... Dwarf elliptical galaxy or "dE", in astronomy. Dynamics Explorer, a NASA satellite mission ...