fervidness vs ardor

fervidness and ardor both are nouns.

Word	Noun	Adjective	Verb	Adverb
fervidness	Yes	No	No	No
ardor	Yes	No	No	No

As nouns, fervidness and ardor are synonyms defined as:

Other synonyms of fervidness include ardour, fervency, fervor, fervour, fire.

fervidness (noun)	ardor (noun)
feelings of great warmth and intensity	intense feeling of love
	a feeling of strong eagerness (usually in favor of a person or cause)
	feelings of great warmth and intensity