timer vs timekeeper

timer and timekeeper both are nouns.

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

As nouns, timekeeper is a hypernym of timer; that is, timekeeper is a word with a broader meaning than timer:

Other hypernyms of timer include horologe, timepiece.

As nouns, timer and timekeeper are synonyms defined as:

timer and timekeeper: (sports) an official who keeps track of the time elapsed

timer (noun)	timekeeper (noun)
a timepiece that measures a time interval and signals its end	a measuring instrument or device for keeping time
a regulator that activates or deactivates a mechanism at set times	a clerk who keeps track of the hours worked by employees
(sports) an official who keeps track of the time elapsed	(sports) an official who keeps track of the time elapsed