shading vs marking

shading and marking both are nouns.

Word	Noun	Adjective	Verb	Adverb
shading	Yes	No	No	No
marking	Yes	No	No	No

As nouns, marking is a hypernym of shading; that is, marking is a word with a broader meaning than shading:

shading: graded markings that indicate light or shaded areas in a drawing or painting
marking: a pattern of marks

shading (noun)	marking (noun)
a gradation involving small or imperceptible differences between grades	evaluation of performance by assigning a grade or score
graded markings that indicate light or shaded areas in a drawing or painting	the act of making a visible mark on a surface
	a pattern of marks
	a distinguishing symbol