The rate at which customers or revenue are lost; usually a symptom of an upstream problem.
Churn is the rate at which customers (logo churn) or revenue (revenue churn) are lost over a period. Churn is almost always a symptom rather than a root cause - of poor onboarding, weak value realization, or a misfit customer acquired in the first place. Reducing it starts with early-warning signals and the right ownership of the account.