Flashcard answers should be 1–5 words for most facts. Anything longer is a signal that the card is testing more than one thing, or that the question is too broad. Shorter answers are easier to evaluate — which is the whole point of using flashcards in a spaced repetition system.
Why Shorter Is Better
When you flip a card and the answer is a sentence, you’re left guessing whether you “got it” or not. With a 1–3 word answer, you know immediately. That clarity drives the correct/wrong decision that makes the Leitner system work accurately.
Exceptions
Some answers legitimately require more words — a chemical formula, a multi-part sequence, a foreign-language sentence for translation. In these cases, accept up to a sentence — but ensure the question is still specific and the answer is exactly what you intended. Use the quality checklist to evaluate borderline cards.
How to Trim a Long Answer
Ask: what is the one piece of information this card is actually testing? Write only that. If the rest is also important, it gets its own card. This forces clarity in your thinking, which strengthens encoding and makes reviews faster.
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