A theory of explanation might treat explanations in either a realist or an epistemic (that is, anti-realist) sense. A realist interpretation of explanation holds that the entities or processes an explanation posits actually exist--the explanation is a literal description of external reality.
Officers in pay grades O-1, O-2, and O-3 with more than four years of prior cumulative service in an enlisted or warrant officer grade are paid increased wages using the special pay grades of O-1E, O-2E, and O-3E, respectively.
Pay grades are divided into three groups: enlisted (E), warrant officer (W), and officer (O). Enlisted pay grades begin at E-1 and end at E-9; warrant officer pay grades originate at W-1 and terminate at W-5; and officer pay grades start at O-1 and finish at O-11.