flashcard vs poster

flashcard and poster both are nouns.

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

As nouns, poster is a hypernym of flashcard; that is, poster 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
poster: a sign posted in a public place as an advertisement

Other hypernyms of flashcard include bill, card, notice, placard, posting.

flashcard (noun)	poster (noun)
a card with words or numbers or pictures that is flashed to a class by the teacher	a horse kept at an inn or post house for use by mail carriers or for rent to travelers
	a sign posted in a public place as an advertisement
	someone who pastes up bills or placards on walls or billboards