# Prefixes

Prefixes are useful for expressing units of physical quantities that are either very big or very small.

Some of the Greek prefixes and their symbols to indicate decimal sub-multiples and multiples of the SI units are:

Number Prefix
NumberPrefixNumberPrefix
$10^{-9}$nano (n)$10^{-1}$deci (d)
$10^{-6}$micro ($\mu$)$10^{3}$Kilo (K)
$10^{-3}$milli (m)$10^{6}$Mega (M)
$10^{-2}$centi (c)$10^{9}$Giga (G)

Common examples:

• 1 cm = 0.01 metre
• 1 kg = 1000 grams
• 1 GB = 1 000 000 000 bytes

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