The prefixes used within the metric system serve to designate a multiple or subdivision of a unit. The most common prefixes include: mega-, kilo-, centi-, milli- and nano-. All prefixes designate a power of 10.
The metric system has been adopted by the majority of the world and uses one fundamental unit for every quantity. Prefixes are attached to the fundamental unit for very large or very small numbers. For example, 1,000 meters is more easily represented as 1 kilometer. Conversely, 0.001 grams is more easily represented as 1 milligram. The one-letter abbreviations for the prefixes are case sensitive. For example, capital "M" is the abbreviation for mega-, while lowercase "m" is the abbreviation for milli-.