simple vs undecomposable

simple is a noun but undecomposable is not a noun.

Word	Noun	Adjective	Verb	Adverb
simple	Yes	Yes	No	No
undecomposable	No	Yes	No	No

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

simple (adjective)	undecomposable (adjective)
(botany) of leaf shapes; of leaves having no divisions or subdivisions	representing the furthest possible extent of analysis or division into parts
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