melanism vs melanosis

melanism and melanosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
melanism	Yes	No	No	No
melanosis	Yes	No	No	No

As nouns, melanism and melanosis are synonyms defined as:

melanism and melanosis: a condition characterized by abnormal deposits of melanin (especially in the skin)

melanism (noun)	melanosis (noun)
a condition characterized by abnormal deposits of melanin (especially in the skin)	a condition characterized by abnormal deposits of melanin (especially in the skin)