flashcard vs placard

flashcard and placard both are nouns.

Word	Noun	Adjective	Verb	Adverb
flashcard	Yes	No	No	No
placard	Yes	No	Yes	No

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

flashcard: 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 flashcard include bill, card, notice, poster, posting.

flashcard (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

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