similarity vs sameness

similarity and sameness both are nouns.

Word	Noun	Adjective	Verb	Adverb
similarity	Yes	No	No	No
sameness	Yes	No	No	No

As nouns, sameness is a hypernym of similarity; that is, sameness is a word with a broader meaning than similarity:

similarity (noun)	sameness (noun)
the quality of being similar	the quality of being alike
a Gestalt principle of organization holding that (other things being equal) parts of a stimulus field that are similar to each other tend to be perceived as belonging together as a unit	the quality of wearisome constancy, routine, and lack of variety