largeness vs greatness

largeness and greatness both are nouns.

Word	Noun	Adjective	Verb	Adverb
largeness	Yes	No	No	No
greatness	Yes	No	No	No

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

largeness (noun)	greatness (noun)
the property of having a relatively great size	the property possessed by something or someone of outstanding importance or eminence
large or extensive in breadth or importance or comprehensiveness	unusual largeness in size or extent or number
the quality of being pretentious (behaving or speaking in such a manner as to create a false appearance of great importance or worth)
the capacity to understand a broad range of topics