prepositional vs preposition

prepositional is not a noun while preposition is a noun.

Word	Noun	Adjective	Verb	Adverb
prepositional	No	Yes	No	No
preposition	Yes	No	No	No

prepositional (noun)	preposition (noun)
	a function word that combines with a noun or pronoun or noun phrase to form a prepositional phrase that can have an adverbial or adjectival relation to some other word
	(linguistics) the placing of one linguistic element before another (as placing a modifier before the word it modifies in a sentence or placing an affix before the base to which it is attached)

prepositional (adjective)	preposition (adjective)
of or relating to or formed with a preposition