observer vs actor

observer and actor both are nouns.

Word	Noun	Adjective	Verb	Adverb
observer	Yes	No	No	No
actor	Yes	No	No	No

As nouns, actor is a hypernym of observer; that is, actor is a word with a broader meaning than observer:

observer: a person who becomes aware (of things or events) through the senses
actor: a person who acts and gets things done

Other hypernyms of observer include doer, worker.

observer (noun)	actor (noun)
a person who becomes aware (of things or events) through the senses	a theatrical performer
an expert who observes and comments on something	a person who acts and gets things done