On this page
  1. Why we forget, and why reviews help
  2. How a spaced repetition app decides when you see a word
  3. Why Chinese needs more than one schedule
  4. Tips that make it work
  5. Questions and answers
  6. Sources

Short answer Spaced repetition means you review a word just before you would forget it. Each time you remember it, the next review moves further out: from minutes to days, then weeks and months. You spend your time on the words you are about to lose, not on the ones you already know.

Why we forget, and why reviews help

In the 1880s, the psychologist Hermann Ebbinghaus learned lists of nonsense syllables and tested himself after different delays. He found that most of what we learn fades quickly at first and then more slowly. This pattern is now called the forgetting curve. Each review flattens the curve: the memory lasts longer before it fades again.

Two findings from memory research make spaced repetition work:

  • Spacing beats cramming. A large review of hundreds of experiments (Cepeda and colleagues, 2006) found that spreading reviews over time leads to better long-term memory than the same amount of study in one block.
  • Recalling beats rereading. Trying to remember an answer before you see it strengthens memory more than reading it again (Roediger and Karpicke, 2006). That is why flashcards show the question first.
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How a spaced repetition app decides when you see a word

You see a word and try to recall it. Then you rate how it went: Again, Hard, Good or Easy. The app uses your rating to estimate how well you know the word and picks the next review date.

  • Again: you see the word again soon, often in the same session.
  • Good: the gap grows, for example from one day to a few days, later to weeks.
  • Easy: the gap grows even more.

Older apps use fixed formulas such as SM-2, which SuperMemo introduced in 1987 and Anki used for many years. Newer schedulers learn from your answers. FSRS (Free Spaced Repetition Scheduler) is an open-source scheduler that Anki has offered since version 23.10. It estimates for each card how likely you are to remember it today and schedules the review when that chance drops to a target, often 90%.

Why Chinese needs more than one schedule

With Chinese, knowing a word means three different things: you read the characters, you understand the word when you hear it, and you write it. These skills do not grow together. Many learners can read 认识 but cannot write it from memory, or recognise 舒服 on paper but miss it in a conversation.

That is why Hanzi By Heart reviews each word three ways, reading, listening and writing, and gives each skill its own schedule. It uses FSRS-6 with a 90% target. If you can read a word but not write it, the writing card comes back sooner, while the reading card waits.

Tips that make it work

  • Review every day, even for 10 minutes. Short daily sessions beat one long session per week.
  • Rate honestly. Pressing Good when you guessed only makes the word come back too late.
  • Add new words at a steady pace. Every new word brings reviews in the following days. If your reviews pile up, add fewer new words for a few days.
  • Learn words with a sentence. An example sentence shows how a word is used and gives you more to remember it by.

Questions and answers

Is spaced repetition better than cramming? For long-term memory, yes. Cramming can help for a test tomorrow, but spaced reviews keep the words for months.

How long does it take each day? That depends on how many new words you add. Many learners do 15–30 minutes a day.

Do I need Anki? No. Anki is a flexible tool if you like to build your own decks. Apps such as Hanzi By Heart come with ready-made HSK word lists, audio and handwriting practice.

What does a 90% target mean? The app schedules a review when it expects you to still remember the word with a 90% chance. A higher target means more reviews; a lower one means more forgetting.

Sources