comprehend vs ache

comprehend is not a noun while ache is a noun.

Word	Noun	Adjective	Verb	Adverb
comprehend	No	No	Yes	No
ache	Yes	No	Yes	No

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

comprehend (noun)	ache (noun)
	a dull persistent (usually moderately intense) pain

comprehend (verb)	ache (verb)
get the meaning of something	have a desire for something or someone who is not present
to become aware of through the senses	be the source of pain
include in scope; include as part of something broader; have as one's sphere or territory	feel physical pain