enclosing class meaning in English

封闭类
外围类别与巢状类别

Visible only within the project for nested classes , within the enclosing class
仅在项目内可见（对于嵌套的类，在包含类内可见）
An explicit specialization shall be declared in the namespace of which the template is a member , or , for member templates , in the namespace of which the enclosing class or enclosing class template is a member
一个显式的特化应该声明在它所在的名域中,对于成员模板来说,应该在声明于它所嵌的类所在的名域中。