watcher vs patroller

watcher and patroller both are nouns.

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

As nouns, patroller is a hyponym of watcher; that is, patroller is a word with a more specific, narrower meaning than watcher:

watcher: a guard who keeps watch
patroller: someone on patrol duty; an individual or a member of a group that patrols an area

watcher (noun)	patroller (noun)
a guard who keeps watch	someone on patrol duty; an individual or a member of a group that patrols an area
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