Create your own decks of flashcards right on your phone. You can then study where and whenever you like.
Tell the app which cards you got right and wrong. Using an algorithm based on the Leitner system, cards will appear with varying frequency depending on how well you know them. Those you find harder will appear more often.
You can reverse the direction of play, so that you learn the cards in both directions (e.g. English-to-French and French-to-English).
Card decks can be used to help you learn all subjects, including:
Language Vocabulary
Keyword Definitions
Countries & Capitals
Historic Events & Years
.... and anything else you can imagine.