sights vs optical instrument

sights and optical instrument both are nouns.

Word	Noun	Adjective	Verb	Adverb
sights	Yes	No	No	No
optical instrument	Yes	No	No	No

As nouns, optical instrument is a hypernym of sights; that is, optical instrument is a word with a broader meaning than sights:

sights: an optical instrument for aiding the eye in aiming, as on a firearm or surveying instrument
optical instrument: an instrument designed to aid vision

sights (noun)	optical instrument (noun)
an optical instrument for aiding the eye in aiming, as on a firearm or surveying instrument	an instrument designed to aid vision