ontology vs ontological

ontology is a noun but ontological is not a noun.

Word	Noun	Adjective	Verb	Adverb
ontology	Yes	No	No	No
ontological	No	Yes	No	No

ontology (noun)	ontological (noun)
the metaphysical study of the nature of being and existence
(computer science) a rigorous and exhaustive organization of some knowledge domain that is usually hierarchical and contains all the relevant entities and their relations

ontology (adjective)	ontological (adjective)
	of or relating to ontology