vowel gradation

noun

1. the act or process of forming or arranging in grades, stages, or steps
2. a gradual change by steps or stages from one condition, quality, etc. to another
3. a gradual shading of one tint, tone, or color into another
4. a step, stage, or degree in a graded series; transitional stage: the many gradations between good and bad
5. Geol. the process of wearing away high areas of land by erosion and building up low areas by deposition
6. Linguis. ablaut
   in full vowel gradation

Origin: Fr < L gradatio < gradatus, having steps or grades < gradus: see grade