watcher vs perceiver

watcher and perceiver both are nouns.

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

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

watcher: a close observer; someone who looks at something (such as an exhibition of some kind)
perceiver: a person who becomes aware (of things or events) through the senses

Other hypernyms of watcher include beholder, observer, percipient.

watcher (noun)	perceiver (noun)
a guard who keeps watch	a person who becomes aware (of things or events) through the senses
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