DUPLICATE, adjective [Latin , to double; twofold; 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.

DUPLICATE, noun

1. Another corresponding to the first; or a second thing of the same kind.

2. A copy; a transcript. Thus a second letter or bill of exchange exactly like the first is called a duplicate

DUPLICATE, verb transitive [Latin] To double; to fold.