spacing vs compactness

spacing and compactness both are nouns.

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

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

spacing: the property possessed by an array of things that have space between them
compactness: the spatial property of being crowded together

Other hyponyms of spacing include openness, distance, dispersion, distribution, concentration, denseness, density, tightness.

spacing (noun)	compactness (noun)
the property possessed by an array of things that have space between them	the spatial property of being crowded together
the time between occurrences of a repeating event	the consistency of a compact solid