auditor vs observer

auditor and observer both are nouns.

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

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

auditor: someone who listens attentively
observer: a person who becomes aware (of things or events) through the senses

Other hypernyms of auditor include beholder, perceiver, percipient.

auditor (noun)	observer (noun)
a qualified accountant who inspects the accounting records and practices of a business or other organization	a person who becomes aware (of things or events) through the senses
someone who listens attentively	an expert who observes and comments on something
a student who attends a course but does not take it for credit