oil stain vs discoloration

oil stain and discoloration both are nouns.

Word	Noun	Adjective	Verb	Adverb
oil stain	Yes	No	No	No
discoloration	Yes	No	No	No

As nouns, discoloration is a hypernym of oil stain; that is, discoloration is a word with a broader meaning than oil stain:

Other hypernyms of oil stain include discolouration, stain.

oil stain (noun)	discoloration (noun)
a stain produced by oil	the act of changing the natural color of something by making it duller or dingier or unnatural or faded
	a soiled or discolored appearance