What is the meaning of Gradation?

A sequence of gradual, successive stages; a systematic progression.

A passing by small degrees from one tone or shade, as of color, to another.

The act of gradating or arranging in grades.

Any degree or relative position in an order or series.

A calibration marking.

A gradual change within one parameter, or an overlapping of two blocks of sound.

A diatonic succession of chords.

Ablaut.

To form with gradations.

gradation

Source: wiktionary.org