ISO 80000-1:2009 is a standard describing scientific and mathematical quantities and their units. The standard, whose full name is Quantities and units Part 1: General was developed by the International Organization for Standardization (ISO), superseding ISO 31-0. It provides general information concerning quantities and units and their symbols, especially the International System of Quantities and the International System of Units, and defines these quantities and units. It is a part of a group of standards called ISO/IEC 80000.
The standard is divided into the following chapters:
- Normative references
- Terms and definitions
- Printing rules
- Annex A (normative) – Terms in names for physical quantities
- Annex B (normative) – Rounding of numbers
- Annex C (normative) – Logarithmic quantities and their units
- Annex D (informative) – International organizations in the field of quantities and units
Quantity, unit and numerical value
It provides the following definitions for quantity, unit and numerical value.
- quantity: property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed by means of a number and a reference
- unit: real scalar quantity, defined and adopted by convention, with which any other quantity of the same kind can be compared to express the ratio of the second quantity to the first one as a number
- numerical value: number in the expression of a quantity value, other than any number serving as the reference
International System of Units
Annex C introduces the concepts of power quantities and root-power quantities.