isr.co.ro : glossary Hierarchy A logical structure that arranges elements in a series of branches starting from a root or top-level node. Each node can have none, one, or several branches leading to subsidiary nodes, which in turn can have their own branches. But there's always just one and only one path from any lower-level node back up to the root. Many elements of the Internet are organized in hierarchies, including the Domain Name System (DNS), the directory structures of most host and user computers, the Usenet newsgroups, and of course the organization charts of many of the organizations that use the system.