n.

1. 逐渐的变化；阶段性变化[C][U]
   the gradations of color in the rainbow

   彩虹颜色的逐渐变化

2. （变化的）阶段，程度；（颜色的）层次[P1]
   A good actor can express every gradation of feeling from joy to grief.

   一名好演员能够表现出由快乐至痛苦的每一阶段的感情变化。

   There are many gradations between good and bad.

   在好与坏之间还有许多不同的层次。

n.

1. a scale of successive changes, stages, or degrees.
   ▸a stage in such a scale.
2. a minute change from one shade, tone, or colour to another.
3. Linguistics  another term for ablaut.