posting vs flash card

posting and flash card both are nouns.

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

As nouns, flash card is a hyponym of posting; that is, flash card is a word with a more specific, narrower meaning than posting:

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

Other hyponyms of posting include show bill, show card, theatrical poster, flashcard.

posting (noun)	flash card (noun)
the transmission of a letter	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
(bookkeeping) a listing on the company's records