melanosis vs melanism

melanosis and melanism both are nouns.

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

As nouns, melanosis and melanism are synonyms defined as:

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

melanosis (noun)	melanism (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)