simple vs kidney-shaped

simple is a noun but kidney-shaped is not a noun.

Word	Noun	Adjective	Verb	Adverb
simple	Yes	Yes	No	No
kidney-shaped	No	Yes	No	No

simple (noun)	kidney-shaped (noun)
a person lacking intelligence or common sense
any herbaceous plant having medicinal properties

simple (adjective)	kidney-shaped (adjective)
(botany) of leaf shapes; of leaves having no divisions or subdivisions	(of a leaf or bean shape) resembling the shape of kidney
having few parts; not complex or complicated or involved
easy and not involved or complicated
exhibiting childlike simplicity and credulity
unornamented
lacking mental capacity and subtlety
apart from anything else; without additions or modifications