fervidness vs ardour

fervidness and ardour both are nouns.

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

As nouns, fervidness and ardour are synonyms defined as:

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

fervidness (noun)	ardour (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