passion vs ardour

passion and ardour both are nouns.

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

As nouns, ardour is a hyponym of passion; that is, ardour is a word with a more specific, narrower meaning than passion:

Other hyponyms of passion include infatuation, abandon, wildness, ardor, fervency, fervidness, fervor, fervour, fire, storminess.

passion (noun)	ardour (noun)
the trait of being intensely emotional	intense feeling of love
any object of warm affection or devotion	a feeling of strong eagerness (usually in favor of a person or cause)
a strong feeling or emotion	feelings of great warmth and intensity
a feeling of strong sexual desire
an irrational but irresistible motive for a belief or action
something that is desired intensely