"Kindle" Index Cards?

Is there any electronic index cards format available? It would be quicker than paper index cards and easily sorted by subject matter, alphabetically and so forth. I’m thinking of index cards used for memorization although there could be other uses such as storing cooking recipes.

I don’t know of any for the Kindle specifically, but there are dozens for Android and iOS. Just a quick google search of “android index card” returned dozens of results.