What is SI system of units?

Answer 1

The SI system of units is the international system of measurements. It is also known as the "metric system", although technically there are different (but similar) metric systems. The SI system is used in most countries in the world; both scientists and common people generally use SI units such as meter, kilogram, second, square meter, etc.; some common exceptions to this are units of time (the official unit is the second, but other units are used as well), speed (the official unit is meters/second, but kilometers/hour are quite common), and temperature (the official unit is the Kelvin, but the degree Celsius is more common in a non-scientific context).