FQDN (fully qualified domain name)

A Domain Name System (DNS) that has been stated unambiguously to indicate with certainty its location in the domain namespace tree. Fully qualified domain names differ from relative names in that they typically are stated with a trailing period (.), for example, "host.example.microsoft.com.", to qualify their position to the root of the namespace. [Exchange 2003]

A DNS name that has been stated to indicate its absolute location in the domain namespace tree. In contrast to relative names, an FQDN has a trailing period (.) to qualify its position to the root of the namespace (host.example.microsoft.com.). [Exchange 2007]