tarnish vs stain

tarnish and stain both are nouns.

Word	Noun	Adjective	Verb	Adverb
tarnish	Yes	No	Yes	No
stain	Yes	No	Yes	No

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

Other hypernyms of tarnish include discoloration, discolouration.

As verbs, tarnish and stain are synonyms defined as:

tarnish and stain: make dirty or spotty, as by exposure to air; also used metaphorically

Other synonyms of tarnish include defile, maculate, sully.

tarnish (noun)	stain (noun)
discoloration of metal surface caused by oxidation	an act that brings discredit to the person who does it
	a soiled or discolored appearance
	a symbol of disgrace or infamy
	anything regarded as making something unclean
	(microscopy) a dye or other coloring material that is used in microscopy to make structures visible

tarnish (verb)	stain (verb)
make dirty or spotty, as by exposure to air; also used metaphorically	produce or leave stains
	color with a liquid dye or tint
	color for microscopic study
	make dirty or spotty, as by exposure to air; also used metaphorically