retention rate → ποσοστό διατήρησης, ποσοστό διατήρησης πελατών, ποσοστό διατήρησης κοινού, ποσοστό διατήρησης συνδρομητών, ποσοστό συγκράτησης, ποσοστό διατήρησης θεραπείας
The term "retention rate" is used in a variety of fields, including marketing, investing, education, in the workplace and in clinical trials. Maintaining retention in each of these fields often results in a positive outcome for the overall organization or school, or pharmacological study. In marketing, retention rate is used to count customers and track customer activity irrespective of the number of transactions (or dollar value of those transactions) made by each customer.
https://en.wikipedia.org/wiki/Retention_rate