prince vs princeling

prince and princeling both are nouns.

Word	Noun	Adjective	Verb	Adverb
prince	Yes	No	No	No
princeling	Yes	No	No	No

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

prince: a male member of a royal family other than the sovereign (especially the son of a sovereign)
princeling: a young prince

prince (noun)	princeling (noun)
a male member of a royal family other than the sovereign (especially the son of a sovereign)	a young prince
	a petty or insignificant prince who rules some unimportant principality