Gradation /(?)/

Gra·da·tion

Gradation

The act of progressing by regular steps or orderly arrangement; the state of being graded or arranged in ranks; as, the gradation of castes.
The act or process of bringing to a certain grade.
Any degree or relative position in an order or series.
The several gradations of the intelligent universe.
— I. Taylor.
A gradual passing from one tint to another or from a darker to a lighter shade, as in painting or drawing. (Fine Arts)
A diatonic ascending or descending succession of chords. (Mus.)

v. t.