/ grəˈdeɪʃn; NAmE / noun
1.
[ C , U ] ( formal ) any of the small changes or levels which sth is divided into; the process or result of sth changing gradually :
gradations of colour
gradation in size
2.
(also gradu·ation ) [ C ] a mark showing a division on a scale :
the gradations on a thermometer
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WORD ORIGIN
mid 16th cent.: from Latin gradatio(n-) , based on gradus step.