She informed me that she had been promoted to department chief.

chief 是名词，意思是"首领、主管"，指某个部门或组织的最高负责人。这个词来自古法语，原意是"头、首脑"，引申为"领导者"。 在职位名称中，chief 通常表示该部门或领域的最高管理者，如 police chief（警察局长）、fire chief（消防队长）等。