A cohort is a group defined by behaviour rather than by a fixed list.
Defining one
Describe what someone must have done — and not done — to belong. Membership is evaluated when you use it, so a cohort stays current without maintenance.
Using them
Anywhere a filter or breakdown is accepted: funnels, retention, insights.
Useful ones
- Activated — completed the action that predicts sticking around
- At risk — was active, then stopped
- Power users — well above typical usage
The first is the one worth defining carefully; most other analysis is better when split by it.