hierarchy
/ˈhaɪərɑ:kɪ; `haɪəˌrɑrkɪ/ n
system with grades of authority or status from the lowest to the highest 等级制度
She's high up in the management hierarchy. 她在管理阶层中地位很高.
There is a hierarchy in the classification of all living creatures. 一切生物均可按等级分类.