It was intended for use in all fields of science and technology and is augmented by more specialized conventions defined in other parts of the ISO 31 standard.
The presentation here is a summary of some of the detailed guidelines and examples given in the standard.
For example, length, width, diameter and wavelength are all in the same category, that is they are all quantities of the same kind.
In practice, where it is necessary to refer to the numerical value of a quantity expressed in a particular unit, it is notationally more convenient to simply divide the quantity through that unit, as in or equivalently This is a particularly useful and widely used notation for labelling the axes of graphs or for the headings of table columns, where repeating the unit after each numerical value can be typographically inconvenient.
A comprehensive list of internationally standardized mathematical symbols and notations can be found in ISO 31-11.