The metric system is also called the International System of Units (SI), which is a global standard for measurement. The SI system includes seven base units: meter, kilogram, second, mole, kelvin, candela, and ampere. Each unit has several prefixes that represent fractions or multiples of the base unit, such as millimeter or kilogram. Other terms used interchangeably with the metric system include the decimal system, the SI unit system, and the modern measurement system. The metric system is widely used in countries around the world, including the United States, and is considered to be more accurate and efficient than other measurement systems.