timer vs timepiece

timer and timepiece both are nouns.

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

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

Other hypernyms of timer include horologe, timekeeper.

timer (noun)	timepiece (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
(sports) an official who keeps track of the time elapsed