mayor vs civil officer

mayor and civil officer both are nouns.

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

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

Other hypernyms of mayor include politician, civil authority.

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