coldness vs frostiness

coldness and frostiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
coldness	Yes	No	No	No
frostiness	Yes	No	No	No

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

Other hyponyms of coldness include chill, gelidity, iciness, chilliness, coolness, nip, cool.

coldness (noun)	frostiness (noun)
the absence of heat	coldness as evidenced by frost
a lack of affection or enthusiasm	a silvery-white color
the sensation produced by low temperatures