shininess vs sheen

shininess and sheen both are nouns.

Word	Noun	Adjective	Verb	Adverb
shininess	Yes	No	No	No
sheen	Yes	No	No	No

As nouns, shininess and sheen are synonyms defined as:

shininess and sheen: the visual property of something that shines with reflected light

Other synonyms of shininess include luster, lustre.

shininess (noun)	sheen (noun)
the visual property of something that shines with reflected light	the visual property of something that shines with reflected light