; Regional entity The terms Electric Reliability Organization and regional entity have the meanings given those terms in section 215 of the Federal Power Act ( 16 U.S.C. 824o ). (4) Independent System Operator; Regional Transmission Organization The terms Independent System Operator and Regional Transmission Organization have the meanings given those terms in section 3 of the Federal Power Act ( 16 U.S.C. 796 ). (5) Modification The term modification includes a reversal of flow direction, change in ownership, change in flow volume, change in product delivered, addition or removal of an interconnection, or an adjustment to regulate flow (such as a reduction or increase in the number of pump or compressor stations or valves). (6) Natural gas The term natural gas has the meaning given that term in section 2 of the Natural Gas Act ( 15 U.S.C. 717a ). (7) Oil The term oil means petroleum or a petroleum product.