uptime vs 24/7

uptime and 24/7 both are nouns.

Word	Noun	Adjective	Verb	Adverb
uptime	Yes	No	No	No
24/7	Yes	No	No	No

As nouns, 24/7 is a hyponym of uptime; that is, 24/7 is a word with a more specific, narrower meaning than uptime:

uptime: a period of time when something (as a machine or factory) is functioning and available for use
24/7: uptime is 24 hours a day 7 days a week

uptime (noun)	24/7 (noun)
a period of time when something (as a machine or factory) is functioning and available for use	uptime is 24 hours a day 7 days a week