This part of ISO 1998 introduces a list of equivalent English and French terms, in use in the petroleum industry to indicate the measurement of crude oils and petroleum products, together with the corresponding definitions in the two languages. ISO 1998 is intended to cover the purposes of this part of petroleum industry dealing with crude oils and petroleum products, that means all related operations arising from the production field to the final user. It is not intended to cover either petroleum equipment, or any operation in the field. However some pieces of equipment or some operations of exploration and production are defined. The corresponding terms were introduced only when they appear in a definition of a product or process and when their definition was found necessary for understanding or for avoiding any ambiguity. Where a terminology of petroleum equipment is needed, it corresponds to the scope of ISO/TC 67 Materials, equipment and offshore structures for petroleum and natural gas industries.