voyeur vs watcher

voyeur and watcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
voyeur	Yes	No	No	No
watcher	Yes	No	No	No

As nouns, watcher is a hypernym of voyeur; that is, watcher is a word with a broader meaning than voyeur:

voyeur: a viewer who enjoys seeing the sex acts or sex organs of others
watcher: a close observer; someone who looks at something (such as an exhibition of some kind)

Other hypernyms of voyeur include looker, spectator, viewer, witness.

voyeur (noun)	watcher (noun)
a viewer who enjoys seeing the sex acts or sex organs of others	a guard who keeps watch
	a close observer; someone who looks at something (such as an exhibition of some kind)
	a person who keeps a devotional vigil by a sick bed or by a dead body