diachronic (adj.)

before vowels, di-, word-forming element meaning "through, in different directions, between," also often merely intensive, "thoroughly, entirely," from Greek dia "through; throughout," probably cognate with bi- and related to duo "two" (from PIE root *dwo- "two") with a base sense of "twice."

before vowels chron-, word-forming element meaning "time," from Latinized form of Greek khronos "time, a defined time, a lifetime, a season, a while," which is of uncertain origin.