warmness vs soft spot

warmness and soft spot both are nouns.

Word	Noun	Adjective	Verb	Adverb
warmness	Yes	No	No	No
soft spot	Yes	No	No	No

As nouns, soft spot is a hyponym of warmness; that is, soft spot is a word with a more specific, narrower meaning than warmness:

Other hyponyms of warmness include attachment, fond regard, protectiveness, regard, respect.

warmness (noun)	soft spot (noun)
the quality of having a moderate degree of heat	a place of especial vulnerability
a positive feeling of liking	any membranous gap between the bones of the cranium in an infant or fetus
	a sentimental affection