The International System of Units, also known as the SI system, is the internationally recognized standard system for measuring physical quantities. It is based on seven fundamental units, which are used to derive all other units of measurement. The seven fundamental units are:
Meter (m): The unit of length, defined as the distance traveled by light in a vacuum during a specific fraction of a second.Kilogram (kg): The unit of mass, defined as the mass of a specific platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures in France.Second (s): The unit of time, defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.Ampere (A): The unit of electric current, defined as the constant current that, if maintained in two parallel conductors of infinite length, of negligible circular cross-section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2 x 10^-7 newton per meter of length.Kelvin (K): The unit of thermodynamic temperature, defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.Mole (mol): The unit of amount of substance, defined as the amount of substance that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12.Candela (cd): The unit of luminous intensity, defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
The SI system also includes derived units, which are formed by combining the fundamental units using mathematical operations. For example, the unit of velocity is meters per second (m/s), which is derived from the fundamental units of length and time.
The SI system is used in many fields of science and engineering, including physics, chemistry, biology, and electronics. It provides a common standard for measuring physical quantities, which facilitates communication and comparison of data between different regions and disciplines.
