ardour vs fervidness

ardour and fervidness both are nouns.

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

As nouns, ardour and fervidness are synonyms defined as:

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

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