flash card vs posting

flash card and posting both are nouns.

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

As nouns, posting is a hypernym of flash card; that is, posting 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
posting: a sign posted in a public place as an advertisement

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

flash card (noun)	posting (noun)
a card with words or numbers or pictures that is flashed to a class by the teacher	the transmission of a letter
	a sign posted in a public place as an advertisement
	(bookkeeping) a listing on the company's records