official vs timekeeper

official and timekeeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
official	Yes	Yes	No	No
timekeeper	Yes	No	No	No

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

Other hyponyms of official include football official, linesman, ref, referee, scorekeeper, scorer, dispatcher, starter, timer, ump, umpire.

official (noun)	timekeeper (noun)
someone who administers the rules of a game or sport	a measuring instrument or device for keeping time
a worker who holds or is invested with an office	a clerk who keeps track of the hours worked by employees
	(sports) an official who keeps track of the time elapsed

official (adjective)	timekeeper (adjective)
having official authority or sanction
of or relating to an office
verified officially
(of a church) given official status as a national or state institution
conforming to set usage, procedure, or discipline