slowness vs rustiness

slowness and rustiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
slowness	Yes	No	No	No
rustiness	Yes	No	No	No

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

slowness: unskillfulness resulting from a lack of training
rustiness: ineptitude or awkwardness as a consequence of age or lack of practice

Other hyponyms of slowness include ham-fistedness, ham-handedness, heavy-handedness.

slowness (noun)	rustiness (noun)
a rate demonstrating an absence of haste or hurry	ineptitude or awkwardness as a consequence of age or lack of practice
lack of normal development of intellectual capacities	the condition of being coated or clogged with rust
unskillfulness resulting from a lack of training