The company is concerned about the high employee turnover in the sales department.

turnover 是由动词短语 turn over（翻转、移交）组合而成的名词，字面意思是"翻转过来"，引申为"人员更替、流动"的意思。在商业环境中特指员工离职与新员工入职的循环过程，即"员工流动率"。