Emily Dickinson Lexicon

DU'PLI-CATE, a. [L. duplicatus, from duplico, to double, from duplex, double, twofold; duo, two, and plico, to fold. See Double.]

Double; twofold. Duplicate proportion or ratio, is the proportion or ratio of squares. Thus in geometrical proportion, the first term to the third is said to be in a duplicate ratio of the first to the second, or as its square is to the square of the second. Thus in 2, 4, 8, 16, the ratio of 2 to 8 is a duplicate of that of 2 to 4, or as the square of 2 is to the square of 4.