announcement vs banns

announcement and banns both are nouns.

Word	Noun	Adjective	Verb	Adverb
announcement	Yes	No	No	No
banns	Yes	No	No	No

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

announcement: a public statement containing information about an event that has happened or is going to happen
banns: a public announcement of a proposed marriage

Other hyponyms of announcement include advisory, handout, press release, release, notice, program, programme, wanted notice, wanted poster.

announcement (noun)	banns (noun)
a public statement containing information about an event that has happened or is going to happen	a public announcement of a proposed marriage
a formal public statement