A forest is a set of one or more domain trees that do not form a contiguous namespace. All trees in a forest share a common schema, configuration, and global catalog. All trees in a given forest trust each other according to transitive hierarchical Kerberos trust relationships. Unlike trees, a forest does not require a distinct name. A forest exists as a set of cross-reference objects and Kerberos trust relationships known to the member trees. Trees in a forest form a hierarchy for the purposes of Kerberos trust; the tree name at the root of the trust tree refers to a given forest.
The following figure illustrates a forest of non-contiguous namespaces.