dim-witted vs simple

dim-witted is not a noun while simple is a noun.

Word	Noun	Adjective	Verb	Adverb
dim-witted	No	Yes	No	No
simple	Yes	Yes	No	No

As adjectives, dim-witted and simple are synonyms defined as:

Other synonyms of dim-witted include simple-minded.

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

dim-witted (adjective)	simple (adjective)
lacking mental capacity and subtlety	(botany) of leaf shapes; of leaves having no divisions or subdivisions
	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