flash card vs placard

flash card and placard both are nouns.

Word	Noun	Adjective	Verb	Adverb
flash card	Yes	No	No	No
placard	Yes	No	Yes	No

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

flash card: a card with words or numbers or pictures that is flashed to a class by the teacher
placard: a sign posted in a public place as an advertisement

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

flash card (noun)	placard (noun)
a card with words or numbers or pictures that is flashed to a class by the teacher	a sign posted in a public place as an advertisement

flash card (verb)	placard (verb)
	publicize or announce by placards
	post in a public place