forgetful person vs simple

forgetful person and simple both are nouns.

Word	Noun	Adjective	Verb	Adverb
forgetful person	Yes	No	No	No
simple	Yes	Yes	No	No

As nouns, simple is a hypernym of forgetful person; that is, simple is a word with a broader meaning than forgetful person:

Other hypernyms of forgetful person include simpleton.

forgetful person (noun)	simple (noun)
a flighty and disorganized person	a person lacking intelligence or common sense
	any herbaceous plant having medicinal properties

forgetful person (adjective)	simple (adjective)
	(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