gradation
/grəˈdeɪʃn; ɡrə`deʃən/ n
1 [U, C] gradual change from one thing to another （从一事物到另一事物的）渐变
Note the subtle gradation of/in colour in this painting. 注意这幅画中色彩的细微变化.
2 [C] any of the stages or steps into which sth is divided （事物划分的）阶段, 等级
It was hard to understand all the minute gradations of their bureaucracy. 很难弄清楚他们那套官僚体制全部细微的等级分别.
3 [C] mark showing a division on a scale 刻度
the gradations on a thermometer 温度计上的刻度.