A server that serves as the central point in a hierarchical structure of database hosts. In the Internet, for example, root domain name servers (DNSs) are positioned as the authoritative sources of all domain names.The Regional Internet Registries (RIRs) maintain the root servers, to which they post domain names directly. Individual Internet service providers (ISPs) download updates from the root servers. See also database, DNS, Internet, RIR, and server.