einingakerfi

Einingakerfi is a term used to describe a system for defining and using units of measurement for physical quantities. A unit system establishes base units from which other units are derived and provides rules for combining them. The International System of Units (SI) is the most widely used example, designed to be coherent so that derived units can be expressed without additional conversion factors.

In SI, there are seven base units: metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for thermodynamic temperature, mole for amount of substance, and candela for luminous intensity. Derived units are formed from these base units, such as the newton (kg·m/s²) for force or the joule (kg·m²/s²) for energy. A coherent unit system is one in which derived units can be expressed directly in terms of base units without extra multipliers.

Other unit systems exist, such as the centimetre–gram–second (CGS) system and various natural or technical systems used in specialized fields. While SI is the canonical standard in science, industry, and education, alternative systems may still be encountered in historical contexts or specific disciplines.

Historically, the metric system emerged in the late 18th century and evolved through international standardization efforts led by bodies like the International Bureau of Weights and Measures (BIPM). The SI system was formalized in 1960 and has since become the global reference for measurements. In Icelandic usage, einingakerfi generally refers to the system of units in use, with SI serving as the predominant standard in official and educational settings.