FORMULABANK

Prefixes are used for large or small units. When you place a prefix in front of a base unit, you indicate how large or small a part of the unit you have or how many times the base unit you have.

Example:
1000 meters can be written as 1 kilometer.
$\frac{1}{1000}$ of a liter can be written as 1 milliliter.

Often, you will encounter prefixes in abbreviations of units. For example, the length of 1 meter is equal to 100 centimeters. Instead of writing the full words, you can abbreviate them: meter becomes "m" and centi becomes "c". Therefore, you can write 1m = 100cm.

Note that it matters whether you use uppercase or lowercase letters—

1MW (1 megawatt) is not the same as 1mW (1 milliwatt)!

In principle, prefixes can be used in front of any unit, but not all are equally common.

Generally, you should not mix multiple prefixes, but in some cases, such as 1hkg = 1 hectokilogram = 100 kg, it is used.

Some prefixes may be "hidden." The unit of area 1 hectare means 1 hecto-are = 100 ares. 1 are = 100m², so 1 hectare = 100×100m² = 10000m². 1 hectare is abbreviated as 1 ha.

There are many prefixes, but the most common are: