ache vs itch

ache and itch both are nouns.

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

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

Other hyponyms of ache include bite, burn, sting, burn, hunger, thirst, act up, throb, shoot.

ache (noun)	itch (noun)
a dull persistent (usually moderately intense) pain	an irritating cutaneous sensation that produces a desire to scratch
	a strong restless desire
	a contagious skin infection caused by the itch mite; characterized by persistent itching and skin irritation

ache (verb)	itch (verb)
have a desire for something or someone who is not present	have a strong desire or urge to do something
be the source of pain	have or perceive an itch
feel physical pain	scrape or rub as if to relieve itching
	cause to perceive an itch