01 / THE IDEA
What does it mean?
Retention measures how many users from a defined group return or remain active over a specified period.
02 / IN PRACTICE
Make it concrete.
Illustrative example: A note-taking app measures how many new users still create notes four weeks after signup.
03 / WHAT TO WATCH FOR
A common mistake.
Using total visits as a substitute for returning users.
04 / WHEN IT HELPS
When should you use it?
When evaluating whether a product provides repeated value.
05 / FURTHER READING
Explore the source.
Amplitude Docs — Retention calculation ↗A reference for further learning, not an endorsement or verbatim quotation.