upkeep vs mend

upkeep and mend both are nouns.

Word	Noun	Adjective	Verb	Adverb
upkeep	Yes	No	No	No
mend	Yes	No	Yes	No

As nouns, mend is a hypernym of upkeep; that is, mend is a word with a broader meaning than upkeep:

Other hypernyms of upkeep include fix, fixing, fixture, mending, repair, reparation.

upkeep (noun)	mend (noun)
activity involved in maintaining something in good working order	the act of putting something in working order again
the act of sustaining life by food or providing a means of subsistence	sewing that repairs a worn or torn hole (especially in a garment)

upkeep (verb)	mend (verb)
	restore by replacing a part or putting together what is torn or broken
	heal or recover