mayor vs civil authority

mayor and civil authority both are nouns.

Word	Noun	Adjective	Verb	Adverb
mayor	Yes	No	No	No
civil authority	Yes	No	No	No

As nouns, civil authority is a hypernym of mayor; that is, civil authority is a word with a broader meaning than mayor:

Other hypernyms of mayor include politician, civil officer.

mayor (noun)	civil authority (noun)
the head of a city government	a person who exercises authority over civilian affairs