fearfulness vs cowardliness

fearfulness and cowardliness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fearfulness	Yes	No	No	No
cowardliness	Yes	No	No	No

As nouns, cowardliness is a hypernym of fearfulness; that is, cowardliness is a word with a broader meaning than fearfulness:

Other hypernyms of fearfulness include cowardice.

fearfulness (noun)	cowardliness (noun)
the trait of being afraid	the trait of lacking courage
an emotion experienced in anticipation of some specific pain or danger (usually accompanied by a desire to flee or fight)