hereunder vs hereafter

hereunder is not a noun while hereafter is a noun.

Word	Noun	Adjective	Verb	Adverb
hereunder	No	No	No	Yes
hereafter	Yes	No	No	Yes

As adverbs, hereunder and hereafter are synonyms defined as:

hereunder and hereafter: in a subsequent part of this document or statement or matter etc.

Other synonyms of hereunder include hereinafter.

hereunder (noun)	hereafter (noun)
	the time yet to come
	life after death

hereunder (adverb)	hereafter (adverb)
in a subsequent part of this document or statement or matter etc.	in a subsequent part of this document or statement or matter etc.
under the terms of this agreement	following this in time or order or place; after this
	in a future life or state