simple vs simplex

simple is a noun but simplex is not a noun.

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

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

simple (adjective)	simplex (adjective)
(botany) of leaf shapes; of leaves having no divisions or subdivisions	having only one part or element
having few parts; not complex or complicated or involved	allowing communication in only one direction at a time, or in telegraphy allowing only one message over a line at a time
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