great-uncle vs uncle

great-uncle and uncle both are nouns.

Word	Noun	Adjective	Verb	Adverb
great-uncle	Yes	No	No	No
uncle	Yes	No	No	No

As nouns, uncle is a hypernym of great-uncle; that is, uncle is a word with a broader meaning than great-uncle:

great-uncle (noun)	uncle (noun)
an uncle of your father or mother	the brother of your father or mother; the husband of your aunt
	a source of help and advice and encouragement