# Prefixes

## Prefixes for Decimal Multiples and Submultiples

Prefixes are often used for decimal multiples and submultiples of units. Often, the symbols are used together with units. For example, MeV means million electron volts, units of energy. To memorize these prefixes is not something you will enjoy, but if you do know them by heart, you will appreciate the quantity when you encounter them in your reading. You can come back here to check them in case you forgot. The table is arranged in a symmetric fashion for convenience of comparison. Note the increments or decrements by thousand 10+3 or 10-3 are used aside from hecto (centi) and deca (deci).

Multiple Name Abbreviation Name Multiple
10+24 yotta Y   y yocto 10-24
10+21 zetta Z   z zepto 10-21
10+18 exa E   a atto 10-18
10+15 peta P   f femto 10-15
10+12 tera T   p pico 10-12
10+9 giga G   n nano 10-9
10+6 mega M   m micro 10-6
10+3 kilo k   m milli 10-3
10+2 hecto h   c centi 10-2
10+1 deca da   d deci 10-1

When you want to express some large or small quantities, you may also find these prefixes useful.

## Greek Prefixes

Greek prefixes are often used for naming compounds. You will need the prefixes in order to give a proper name of many compounds. You also need to know them to figure out the formula from their names. The common prefixes are given in this Table.

Note that some of the prefixes may change slightly when they are applied to the names. Some of the examples show the variations.

Note also that some names are given using other conventions. For example, $$\ce{P4O6}$$ and $$\ce{P4O10}$$ are called phosphorus trioxide and phosphorus pentoxide respectively. These are given according to their empirical formulas.

Prefix Number Example
mono- 1 monoatomic ions
bi- or di- 2 bicarbonate
dichloro-
tri- 3 tridentate ligand
trinitrotoluene
tetra- 4 ethylenediamine-
tetraacetate