thinning vs dilution

thinning and dilution both are nouns.

Word	Noun	Adjective	Verb	Adverb
thinning	Yes	No	No	No
dilution	Yes	No	No	No

As nouns, dilution is a hypernym of thinning; that is, dilution is a word with a broader meaning than thinning:

thinning: the act of diluting something
dilution: weakening (reducing the concentration) by the addition of water or a thinner

thinning (noun)	dilution (noun)
the act of diluting something	weakening (reducing the concentration) by the addition of water or a thinner
	a diluted solution