standby vs actor

standby and actor both are nouns.

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

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

Other hypernyms of standby include histrion, player, role player, thespian.

standby (noun)	actor (noun)
something that can be relied on when needed	a theatrical performer
an actor able to replace a regular performer when required	a person who acts and gets things done

standby (adjective)	actor (adjective)
ready for emergency use