grading vs rating

grading and rating both are nouns.

Word	Noun	Adjective	Verb	Adverb
grading	Yes	No	No	No
rating	Yes	No	No	No

As nouns, rating is a hypernym of grading; that is, rating is a word with a broader meaning than grading:

Other hypernyms of grading include evaluation.

grading (noun)	rating (noun)
the act of arranging in a graduated series	act of ascertaining or fixing the value or worth of
evaluation of performance by assigning a grade or score	an appraisal of the value of something
changing the ground level to a smooth horizontal or gently sloping surface	standing or position on a scale
	rank in a military organization