Review interval

A review interval is the time between one review of an item and the next.

There is no universal interval for every learner or opening. A schedule can shorten the gap after a miss and extend it after successful recall.

The interval is the gap between attempts

An interval begins after one review and ends when the same item appears again. It can be measured in hours, days, or weeks; the number matters only in relation to the learner and the retention goal.

Successful recall can support a longer interval

A missed or guessed move is evidence that the current memory is unstable, so the next review can return sooner. Repeated successful recall supports a longer delay, which reduces unnecessary review of material that is already available.

Treat the interval as an estimate

A line may appear in a real game before its scheduled review, and an unfamiliar branch may require an earlier return. The schedule should organize attention without pretending to predict memory perfectly.