The information in this document is limited to aircraft engine fuel feed, refueling, and transfer components. It is assumed that isothermal, liquid fluid conditions exist, herein referred to as fuel. Where a unit of measure is suffixed, this is intended to show a generally associated unit for illustration only and is not an exclusive endorsement of this particular term. Where applicable and allowable it is understood that a referee fluid may be substituted for fuel. The purpose of this document is to define commonly used pressure terms relating to aircraft engine fuel feed, refueling, and transfer components. It is not intended to exclude other pressure terms which may also be appropriate.