Prefixes are used to denote multiples or submultiples of units. PrefixName is the full name of the prefix (e.g., si:kilo). Symbol is the character(s) used to represent the prefix (e.g., 'k'). Factor is the numerical multiplier associated with the prefix (e.g., 1000).

When a prefix is used with a unit (e.g., si:kilo(si:metre)), the library combines the prefix's symbol with the unit's symbol (e.g., "km") and applies the factor to the unit's value. Note that the library won't recognize the concatenated name of the prefix and unit, (e.g. si:kilometre for si:kilo(si:metre). If you want that, you can add an alias units:alias(si:kilometre, si:kilo(si:metre)). The only predefined alias in the library is si:kilogram as it is a base SI unit.

Examples:

units:prefix(si:kilo, 'k', 1000).
units:prefix(si:milli, 'm', 1/1000).
units:prefix(iec:kibi, 'Ki', 1024).

Arguments:

PrefixName	- The full name of the prefix, often namespaced (e.g., si:kilo, iec:mebi).
Symbol	- The symbol for the prefix (e.g., 'k', 'M').
Factor	- The numerical factor the prefix represents (e.g., 1000, 1024*1024).