Term used to describe items that do not concretely fit within an existing node in the hierarchy.
In some cases, an unclassified item may not have a proper category within the existing hierarchy. For instance, a pet food hierarchy with pet-specific nodes like [Dog], [Cat], and [Bird] will not have a proper home for turtle food. In such cases, the turtle food item may be quarantined, a new category may be created, or existing nodes may be updated to be more inclusive of outlying items. Solutions to this issue is dependent on client needs.