# SI Units and Measurement, Science Game

What do we mean by SI units? SI stands for International Systems of Units or in French, Système International (SI) d’Unités. It is an international decimal system of weights and measures derived from the metric system of units. It is international because it enables scientists to communicate units consistently across the globe. Imagine the nightmare of trying to understand different standards of measurement by different countries. So someone had the bright idea to create an international standard for unit measurement. Play this game to learn more about SI units and measurement.

Metric units
Metric and SI systems are two widely-used measurements, although some of them are not recognized by all countries. Before the adoption of the metric system in the 1870s, the gravitational metric system was used in many disciplines. Examples of the SI units used in different disciplines include the kilogram-force, technical atmosphere, metric horsepower, sthene, pieze, and rad. There are also SI-unrecognised metric units, such as the meter-candle, which is used in measuring the speed of light.
Derived units
The International System of Units (SI) has 22 derived units, or scales. Derived units are dimensionless products of base units, such as kilograms, meters, or kilometers. Their names are usually lowercase, but 22 of the units have special names. For example, the unit of volume is defined by length, and the derived unit of speed is a meter per second.
Prefixes
Prefixes are symbols that help to communicate large amounts, such as GigaHertz, which is equal to 3,200 million Hertz. In contrast, smaller numbers are represented by periods, or "nm".
Multiples
To learn more about SI units, check out the International System of Units Standard, or SI for short. This document includes information on SI units, quantities, and recommended SI multiples and submultiples. The SI terminology is also explained, including the concept of dual dimensionality. Below are some of the most common SI prefixes. Listed below are the most commonly used multiples and their corresponding units. The SI units page also offers links to common conversion factors.