lookout vs sentry

lookout and sentry both are nouns.

Word	Noun	Adjective	Verb	Adverb
lookout	Yes	No	No	No
sentry	Yes	No	No	No

As nouns, lookout and sentry are synonyms defined as:

lookout and sentry: a person employed to keep watch for some anticipated event

Other synonyms of lookout include lookout man, picket, scout, sentinel, spotter, watch.

lookout (noun)	sentry (noun)
the act of looking out	a person employed to keep watch for some anticipated event
a structure commanding a wide view of its surroundings
an elevated post affording a wide view
a person employed to keep watch for some anticipated event