itch vs ache

itch and ache both are nouns.

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

As verbs, ache is a hypernym of itch; that is, ache is a word with a broader meaning than itch:

Other hypernyms of itch include hurt, smart.

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

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