beholder vs spotter

beholder and spotter both are nouns.

Word	Noun	Adjective	Verb	Adverb
beholder	Yes	No	No	No
spotter	Yes	No	No	No

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

beholder: a person who becomes aware (of things or events) through the senses
spotter: someone who is the first to observe something

beholder (noun)	spotter (noun)
a person who becomes aware (of things or events) through the senses	someone who is the first to observe something
	a worker employed to apply spots (as markers or identifiers)
	a worker employed at a dry-cleaning establishment to remove spots
	a person employed to keep watch for some anticipated event