itching vs pruritus

itching and pruritus both are nouns.

Word	Noun	Adjective	Verb	Adverb
itching	Yes	No	No	No
pruritus	Yes	No	No	No

As nouns, pruritus is a hyponym of itching; that is, pruritus is a word with a more specific, narrower meaning than itching:

itching: an irritating cutaneous sensation that produces a desire to scratch
pruritus: an intense itching sensation that can have various causes (as by allergies or infection or lymphoma or jaundice etc.)

itching (noun)	pruritus (noun)
an irritating cutaneous sensation that produces a desire to scratch	an intense itching sensation that can have various causes (as by allergies or infection or lymphoma or jaundice etc.)