simple vs shield-shaped

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

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

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

simple (adjective)	shield-shaped (adjective)
(botany) of leaf shapes; of leaves having no divisions or subdivisions	(of a leaf shape) round, with the stem attached near the center of the lower surface rather than the margin (as a nasturtium leaf for example)
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