fervor vs fever

fervor and fever both are nouns.

Word	Noun	Adjective	Verb	Adverb
fervor	Yes	No	No	No
fever	Yes	No	No	No

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

Other hyponyms of fervor include fever pitch, sensation, feverishness.

fervor (noun)	fever (noun)
feelings of great warmth and intensity	a state of nervous excitement
the state of being emotionally aroused and worked up	a rise in the temperature of the body; frequently a symptom of infection