Employee attrition refers to the loss of employees when individuals leave an organization and their roles are not replaced, resulting in a reduced workforce. It is not simply the opposite of employee retention, but could be the outcome of unsuccessful retention efforts or intentional workforce reduction. 

Unlike employee turnover, which assumes departing employees are replaced to maintain headcount, attrition leads to a permanent decrease in staffing levels. Attrition can occur naturally over time or be used strategically by employers to lower payroll costs or reduce headcount without layoffs. When not intentional, high or unmanaged attrition can strain teams, impact productivity, and affect long-term organizational performance.