The principal function of a domain name system (DNS) is to translate human-readable domain names, like www.example.com, into IP addresses that computers use to identify each other on the internet. This process simplifies the user experience, allowing individuals to access websites without needing to remember complex numerical addresses. Essentially, DNS acts as the internet's phonebook, routing requests to the correct servers and ensuring that the user is directed to the appropriate content. Overall, it plays a crucial role in the functionality and efficiency of internet navigation.