A child font size in one selector becomes a parent font size in another selector in the lower level in the hierarchyof selector sets.
其中一个选择器中的子字体大小，将成为处于选择器集合中较低层次的另一个选择器的父字体大小。
2
This hierarchy includes four general types of classes: interfaces for the defined types, interfaces for the actual elements, and implementations for both sets of interfaces.
该层次结构包括四种常规类型的类：用于已定义类型的接口、用于实际元素的接口和这两组接口的实现。
3
The most common way to create a controlled vocabulary is to use commonly found terms to describe setsof information and to arrange those terms into a single, rooted hierarchy. For example.