sheep vs domestic sheep

sheep and domestic sheep both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheep	Yes	No	No	No
domestic sheep	Yes	No	No	No

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

sheep: woolly usually horned ruminant mammal related to the goat
domestic sheep: any of various breeds raised for wool or edible meat or skin

Other hyponyms of sheep include ewe, ram, tup, wether, black sheep, Ovis aries.

sheep (noun)	domestic sheep (noun)
woolly usually horned ruminant mammal related to the goat	any of various breeds raised for wool or edible meat or skin
a docile and vulnerable person who would rather follow than make an independent decision
a timid defenseless simpleton who is readily preyed upon