metaphysics vs ontology

metaphysics and ontology both are nouns.

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

As nouns, ontology is a hyponym of metaphysics; that is, ontology is a word with a more specific, narrower meaning than metaphysics:

Other hyponyms of metaphysics include cosmology.

metaphysics (noun)	ontology (noun)
the philosophical study of being and knowing	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