Definitions:
a particular level of rank, quality, proficiency, or value

a mark indicating the quality of a student's work

a gradient or slope

a variety of cattle produced by crossing with a superior breed

arrange in or allocate to grades; classify or sort

give a mark to (a student or a piece of work).

pass gradually from one level, especially a shade of colour, into another

reduce (a road) to an easy gradient.

cross (livestock) with a superior breed.