mayor vs alcalde

mayor and alcalde both are nouns.

Word	Noun	Adjective	Verb	Adverb
mayor	Yes	No	No	No
alcalde	Yes	No	No	No

As nouns, alcalde is a hyponym of mayor; that is, alcalde is a word with a more specific, narrower meaning than mayor:

Other hyponyms of mayor include ex-mayor, burgomaster, mayoress.

mayor (noun)	alcalde (noun)
the head of a city government	a mayor or chief magistrate of a Spanish town