di- (1)

word-forming element of Greek origin meaning "two, double, twice, twofold," from Greek di-, shortened form of dis "twice," which is related to duo "two" and cognate with bi-, from PIE root *dwo- "two." In chemistry it indicates a compound containing two units of the element or radical to which it is prefixed.

word-forming element of Latin origin meaning "apart, asunder," the form of dis- before certain voiced consonants. As des- was a form of dis- in Old French, some Middle English words have forms in both de- and di-; compare devise, which really belongs to di- and is related to divide.

word-forming element of Greek origin meaning "through; in different directions; between," also often merely intensive, "thoroughly;" the form of dia- before vowels.