Your brain is built to let go of anything it doesn't use. NihaoCard is built to work with that instead of against it.
Within a day, most of it is gone -- unless something brings it back at exactly the right moment.
Straining to recall a word -- not just re-reading it -- is what actually makes it stick.
Not a fixed schedule. Every word, for every student, reviewed right before it would have slipped away.
NihaoCard trains both -- recognizing it, and producing it -- with real sentences, not just definitions.