gradation (n.) Look up gradation at Dictionary.com
1530s, "a climax;" 1670s, "orderly arrangement or succession," from Middle French gradation (16c.) and directly from Latin gradationem (nominative gradatio) "ascent by steps; a climax," noun of action from gradus "step, degree" (see grade (n.)). Meaning "gradual change" is from 1540s.