redoubt vs fastness

redoubt and fastness both are nouns.

Word	Noun	Adjective	Verb	Adverb
redoubt	Yes	No	No	No
fastness	Yes	No	No	No

As nouns, fastness is a hypernym of redoubt; that is, fastness is a word with a broader meaning than redoubt:

Other hypernyms of redoubt include stronghold.

redoubt (noun)	fastness (noun)
an entrenched stronghold or refuge	a strongly fortified defensive structure
(military) a temporary or supplementary fortification; typically square or polygonal without flanking defenses	a rate (usually rapid) at which something happens
	the quality of being fixed in place as by some firm attachment