espy vs sight

espy is not a noun while sight is a noun.

Word	Noun	Adjective	Verb	Adverb
espy	No	No	Yes	No
sight	Yes	No	Yes	No

As verbs, sight is a hypernym of espy; that is, sight is a word with a broader meaning than espy:

Other hypernyms of espy include spy.

espy (noun)	sight (noun)
	the act of looking or seeing or observing
	the ability to see; the visual faculty
	an instance of visual perception
	the range of vision
	a range of mental vision
	a place of interest, especially to visitors
	anything that is seen
	(often followed by `of') a large number or amount or extent

espy (verb)	sight (verb)
catch sight of	catch sight of; to perceive with the eyes
	take aim by looking through the sights of a gun (or other device)