an optical instrument for aiding the eye in aiming, as on a firearm or surveying instrument
"The sniper adjusted the rifle's sights to ensure his shot would hit the target accurately."
plural of sight
"The tourists spent all day taking in the magnificent sights of Paris."
Third-person singular simple present indicative form of sight
"The bird does not sight its prey until it has fully focused on the movement."
In plain English: To see something with your eyes is to sight it, though this word is rarely used as a verb and people usually just say they are looking or watching instead.
"The tour guide will take you to see all the famous sights in Paris over the next few days."