Retention metrics include:
Customer lifetime value (CLV): the average amount of revenue you receive per customer over the entirety of your engagement with them.
Retention rate: the percentage of customers who stay with your company over a given time period; the inverse of churn rate.
Churn rate: how many customers your business loses in a given time period.
Payback period: how long it takes to recover the cost of acquiring a customer.
Product usage: how much and to what extent a customer is using your product. High usage is an indicator of retention.
Customer satisfaction: do your customers feel like your product or service is fulfilling the purpose they purchased it for? If customers are unsatisfied, they are likely to churn.