sundial vs timekeeper

sundial and timekeeper both are nouns.

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

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

sundial: timepiece that indicates the daylight hours by the shadow that the gnomon casts on a calibrated dial
timekeeper: a measuring instrument or device for keeping time

Other hypernyms of sundial include horologe, timepiece.

sundial (noun)	timekeeper (noun)
timepiece that indicates the daylight hours by the shadow that the gnomon casts on a calibrated dial	a measuring instrument or device for keeping time
	a clerk who keeps track of the hours worked by employees
	(sports) an official who keeps track of the time elapsed