postdiluvian vs organism

postdiluvian and organism both are nouns.

Word	Noun	Adjective	Verb	Adverb
postdiluvian	Yes	Yes	No	No
organism	Yes	No	No	No

As nouns, organism is a hypernym of postdiluvian; that is, organism is a word with a broader meaning than postdiluvian:

postdiluvian: anything living after Noah's flood
organism: a living thing that has (or can develop) the ability to act or function independently

Other hypernyms of postdiluvian include being.

postdiluvian (noun)	organism (noun)
anything living after Noah's flood	a living thing that has (or can develop) the ability to act or function independently
	a system considered analogous in structure or function to a living body

postdiluvian (adjective)	organism (adjective)
existing or occurring after Noah's flood