A domain in a domain tree in Microsoft Windows 2000 whose Domain Name System (DNS) name is a subdomain of a parent domain. For example, if the name of the parent or company domain is microsoft.com, some typical names of child domains might include dev.microsoft.com, marketing.microsoft.com, and support.microsoft.com.
New child domains can be created using the Active Directory Installation Wizard. A child domain must be created in an existing domain tree, since creating a new tree automatically creates a new parent domain. A two-way transitive trust exists between a parent domain and its child domains.