noble vs duke

noble and duke both are nouns.

Word	Noun	Adjective	Verb	Adverb
noble	Yes	Yes	No	No
duke	Yes	No	No	No

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

noble (noun)	duke (noun)
a titled peer of the realm	a British peer of the highest rank
	a nobleman (in various countries) of high rank

noble (adjective)	duke (adjective)
having or showing or indicative of high or elevated character
of or belonging to or constituting the hereditary aristocracy especially as derived from feudal times
impressive in size, manner, or appearance
inert especially toward oxygen