fixture vs upkeep

fixture and upkeep both are nouns.

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

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

fixture (noun)	upkeep (noun)
the act of putting something in working order again	activity involved in maintaining something in good working order
an object firmly fixed in place (especially in a household)	the act of sustaining life by food or providing a means of subsistence
the quality of being fixed in place as by some firm attachment
a regular patron