agencymeans— but does not include—
class of positionsincludes all positions which are sufficiently similar, as to— to warrant similar treatment in personnel and pay administration;
employeemeans an individual employed in or under an agency;
gradeincludes all classes of positions which, although different with respect to kind or subject-matter of work, are sufficiently equivalent as to— to warrant their inclusion within one range of rates of basic pay in the General Schedule.
positionmeans the work, consisting of the duties and responsibilities, assignable to an employee;