apprehend vs digest

apprehend is not a noun while digest is a noun.

Word	Noun	Adjective	Verb	Adverb
apprehend	No	No	Yes	No
digest	Yes	No	Yes	No

As verbs, digest is a hyponym of apprehend; that is, digest is a word with a more specific, narrower meaning than apprehend:

Other hyponyms of apprehend include figure, catch on, cotton on, get it, get onto, get wise, latch on, tumble, twig, intuit.

apprehend (noun)	digest (noun)
	something that is compiled (as into a single book or file)
	a periodical that summarizes the news

apprehend (verb)	digest (verb)
get the meaning of something	make more concise
take into custody	systematize, as by classifying and summarizing
anticipate with dread or anxiety	become assimilated into the body
	soften or disintegrate by means of chemical action, heat, or moisture
	soften or disintegrate, as by undergoing exposure to heat or moisture
	arrange and integrate in the mind
	put up with something or somebody unpleasant
	convert food into absorbable substances