solidity vs compactness

solidity and compactness both are nouns.

Word	Noun	Adjective	Verb	Adverb
solidity	Yes	No	No	No
compactness	Yes	No	No	No

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

Other hyponyms of solidity include impermeability, impermeableness.

solidity (noun)	compactness (noun)
the quality of being solid and reliable financially or factually or morally	the spatial property of being crowded together
the consistency of a solid	the consistency of a compact solid
state of having the interior filled with matter