theatrical poster vs placard

theatrical poster and placard both are nouns.

Word	Noun	Adjective	Verb	Adverb
theatrical poster	Yes	No	No	No
placard	Yes	No	Yes	No

As nouns, placard is a hypernym of theatrical poster; that is, placard is a word with a broader meaning than theatrical poster:

Other hypernyms of theatrical poster include bill, card, notice, poster, posting.

theatrical poster (noun)	placard (noun)
a poster advertising a show or play	a sign posted in a public place as an advertisement

theatrical poster (verb)	placard (verb)
	publicize or announce by placards
	post in a public place