length vs shortness

length and shortness both are nouns.

Word	Noun	Adjective	Verb	Adverb
length	Yes	No	No	No
shortness	Yes	No	No	No

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

length: the linear extent in space from one end to the other; the longest dimension of something that is fixed in place
shortness: the property of being of short spatial extent

Other hyponyms of length include circumference, diam, diameter, r, radius, longness.

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

length (noun)	shortness (noun)
a section of something that is long and narrow	an abrupt discourteous manner
the linear extent in space from one end to the other; the longest dimension of something that is fixed in place	the property of being shorter than average stature
continuance in time	the property of being of short temporal extent
the property of being the extent of something from beginning to end	the property of being of short spatial extent
size of the gap between two places	the property of being truncated or short
	the condition of being short of something