The purpose of this standard is to give, in table form, the quantities and mechanical units. When two symbols are given for the same quantity, without special dis inction, they can be used indifferently. SI units are given in bold; other units are given in common characters. The abbreviations "ni, de, en" mean "Dutch, German, Englis " respectively (is 639:1988). The definitions of the units are given in the NBN X 02-001 standard.