8 rules for better flashcards.

A short, practical guide to writing good flashcards for spaced repetition systems like Anki and Repple. Each rule below is illustrated with a worked example.

01

One concept per card

A flashcard should test exactly one thing. If you have to think about which fact you're being asked to recall, the card is doing too much work.

A reliable test: if the answer bundles independent ideas with commas, semicolons, or "and", split it. Tightly paired facts can share a card; unrelated ones can't.

Don't
What is CRISPR-Cas9, and where was it originally discovered?
A programmable DNA-editing tool, originally found in bacterial immune systems.
Do
What is CRISPR-Cas9?
A programmable tool for cutting DNA at specific locations.
Where was CRISPR originally discovered?
Bacterial immune systems, as defense against viral DNA.
02

Keep answers terse

Answers are fragments, not sentences. The question already supplies the context; the answer only needs to add the new information.

Most answers should sit under ten words. Don't restate the question.

Don't
How does TCP ensure reliable delivery?
TCP ensures reliable delivery through acknowledgments and retransmission of lost packets.
Do
How does TCP ensure reliable delivery?
Acknowledgments and retransmission of lost packets.
03

Make every card self-contained

You won't review these cards while reading the textbook. You'll see them months later, in isolation, with no surrounding context.

Replace deictic references with concrete subjects. If the claim is an objective fact, drop the source entirely and ask about the world. If the claim is opinion, argument, or prediction, name the person making it.

Don't
According to the author, why is mass renormalization necessary?
To absorb infinities from self-energy diagrams.
Do
Why is mass renormalization necessary in QED?
To absorb infinities from self-energy diagrams.
Don't
Why should governments run deficits in recessions?
To replace collapsed private demand.
Do
Why does Keynes argue for deficits in recessions?
To replace collapsed private demand.
04

Be concrete: Give the actual fact

Vague answers feel like answers but teach nothing. "Formula relating conditional probabilities" isn't a formula. It's a meta-description: a label for the answer instead of the answer itself.

When the answer is a formula, a definition, or a number, give the formula, definition, or number. Anything less just points at the answer instead of giving it.

Don't
What is Bayes' theorem?
Formula relating conditional probabilities.
Do
What is Bayes' theorem?
Don't
What is compound interest?
Interest that grows over time.
Do
What is compound interest?
Interest paid on past interest, not just the principal.
Don't
What are mitochondria?
The powerhouse of the cell.
Do
What are mitochondria?
Organelles that produce ATP through oxidative phosphorylation.
05

Distill, don't parrot

The textbook chose its phrasing for a different purpose: accuracy in a chapter that builds up the terminology, often with hedges and qualifications. Your card has none of that context.

Cut the hedges and the padding, not the load-bearing terms. The card you can paraphrase aloud is the card you actually understand.

Don't
What does habeas corpus protect against?
The detention of a person by the state without sufficient legal cause being demonstrated before a competent judicial authority.
Do
What does habeas corpus protect against?
Being held by the state without your case being heard in court.
Don't
What is selection bias?
A systematic distortion of statistical results arising when the sample under investigation is not representative of the broader population due to non-random factors influencing inclusion.
Do
What is selection bias?
Results skew because the people you sampled aren't a random slice of the whole population.
06

Don't enumerate

Questions like "What are the three X?" are fragile. Forget one item and you can't tell whether you've actually learned the material or just missed an entry. They test no single concept and bundle several into the same review.

Either split into one card per item, or use a cloze with separate blanks so each piece can be tested independently.

Don't
What are the three branches of the US government?
Executive, legislative, and judicial.
Do
The three branches of the US government are executive, legislative, and judicial.
07

Use cloze for facts, not concepts

Cloze deletions fit a narrow case: a single specific fact you want to recall, like a number, a name, an acronym, or a formula, embedded in a declarative sentence that supplies the context.

Only cloze things worth memorizing exactly. Don't blank conceptual descriptions or whole phrases. That's enumeration in disguise.

Don't
Photosynthesis converts CO₂ and water into glucose using light energy, releasing oxygen.
Do
Photosynthesis converts CO₂ and water into glucose, using light energy and releasing oxygen.
08

Skip orphan facts

Not every fact deserves a card. A good card holds something up: a mechanism, an intuition, a relationship, vocabulary other cards depend on. A card that holds nothing up, and that nothing else leans on, is dead weight in your queue.

The test: if you forgot this card a year from now, would your grasp of the subject genuinely weaken, or would you just lose a stray fact?

Don't
How many cantos make up Dante's Inferno?
34.
Do
How is Dante's Inferno structured?
Nine concentric circles of Hell, each punishing a worse category of sin.

Now go write some cards.

Open Repple and put these principles to use.