ISO 80000-1:2009 gives general information and definitions concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems, especially the International System of Quantities, ISQ, and the International System of Units, SI. The principles laid down in ISO 80000-1:2009 are intended for general use within the various fields of science and technology and as an introduction to other parts of the Quantities and units series. Ordinal quantities and nominal properties are outside the scope of ISO 80000-1:2009.