You must have the appropriate permissions to delete a department. Users with the application-wide Delete Department permission can delete any department in the system. Users with the equivalent department-specific permission are restricted to those departments in which they have this permission.
To delete a department
You can select multiple adjacent departments by holding down the Shift key while clicking the first and last department in the range. To select multiple nonadjacent departments, hold down the Ctrl key while clicking the required departments.