favourite vs lover

favourite and lover both are nouns.

Word	Noun	Adjective	Verb	Adverb
favourite	Yes	Yes	Yes	No
lover	Yes	No	No	No

As nouns, lover is a hypernym of favourite; that is, lover is a word with a broader meaning than favourite:

favourite (noun)	lover (noun)
something regarded with special favor or liking	a person who loves someone or is loved by someone
a special loved one	an ardent follower and admirer
a competitor thought likely to win	a significant other to whom you are not related by marriage

favourite (adjective)	lover (adjective)
preferred above all others and treated with partiality
appealing to the general public

favourite (verb)	lover (verb)
To mark an item as a personal favorite on social media