ardor vs fervidness

ardor and fervidness both are nouns.

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

As nouns, ardor and fervidness are synonyms defined as:

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

ardor (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