| Subject | English | Japanese |
| gen. | Class A river system | 一級水系 |
| gen. | Class B river system | 二級水系 |
| gen. | n class system | 身分制度 |
| abbr. | n class system | 身分制 |
| gen. | n class system | 階級制度 |
| gen. | n class system | 階級性 |
| comp., MS | system class | システム クラス (A class that the CIM Object Manager defines to support core features such as event notification, security, and localization. A system class is automatically defined in each namespace) |