playgoer vs viewer

playgoer and viewer both are nouns.

Word	Noun	Adjective	Verb	Adverb
playgoer	Yes	No	No	No
viewer	Yes	No	No	No

As nouns, viewer is a hypernym of playgoer; that is, viewer is a word with a broader meaning than playgoer:

playgoer: someone who attends the theater
viewer: a close observer; someone who looks at something (such as an exhibition of some kind)

Other hypernyms of playgoer include looker, spectator, watcher, witness.

playgoer (noun)	viewer (noun)
someone who attends the theater	an optical device for viewing photographic transparencies
	a close observer; someone who looks at something (such as an exhibition of some kind)