Which part of a domain name represents the highest level in the hierarchy?

The part of a domain name that represents the highest level in the hierarchy is known as the first-level domain. This level is often referred to as the top-level domain (TLD) and typically is what follows the final dot in a full domain name. Examples of first-level domains include .com, .org, and .net, as well as various country code suffixes such as .uk or .ca.

In the context of hierarchical structure, the first-level domain stands at the apex, signifying the broadest category within the domain name system (DNS). It is crucial to understand that the hierarchy of domain names progresses from the broader category (the TLD) to more specific ones (second-level domains, subdomains), where each subsequent level provides more detail about the specific entity or address being represented. Thus, identifying the first-level domain as the highest level is essential for comprehending how web addresses are organized and categorized.