This Technical Report gives explanation on the pressure definitions used by the gas network operators with regard to the standards of CEN/TC 234 "Gas Infrastructure". The European Standards of CEN/TC 234 comprise the functional requirements in the field of gas infrastructure from the input of gas into the on-shore transmission network up to the inlet connection of gas appliances, including transmission, distribution, storage, compression, pressure regulation and metering, installation, injection of non-conventional gases, gas quality issues and others.