Alusühikust

Alusühikust, often translated as "base unit" or "fundamental unit," refers to the independently defined units upon which a system of measurement is built. In the context of the International System of Units (SI), there are seven base units: the meter for length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for thermodynamic temperature, the mole for amount of substance, and the candela for luminous intensity.

These base units are chosen because they are considered fundamental quantities that cannot be expressed in terms of other quantities. For instance, velocity is a derived quantity, as it is defined as length divided by time (m/s). All other units within the SI system, known as derived units, can be expressed as combinations of these seven base units. Examples of derived units include the newton (force), joule (energy), and watt (power).

The concept of base units ensures consistency and coherence within a measurement system. By defining a minimal set of fundamental units, a complex system of derived units can be logically constructed and understood. This approach simplifies the definition and realization of all units within the system, providing a robust framework for scientific and technological applications worldwide. The SI base units are currently defined by fundamental physical constants.