Standard Prefixes

Mks units are specifically designed to conveniently describe those motions that occur in everyday life. Unfortunately, mks units tend to become rather unwieldy when dealing with motions on very small scales (e.g., the motions of molecules) or on very large scales (e.g., the motions of stars in the Milky Way galaxy). In order to help cope with this problem, a set of standard prefixes has been devised that allow the mks units of length, mass, and time to be modified so as to deal more easily with very small and very large quantities. These prefixes are specified in Table 1.2. Thus, a kilometer (km) represents $10^{\,3}$ m, a nanometer (nm) represents $10^{-9}$ m, and a femtosecond (fs) represents $10^{-15}$ s. The standard prefixes can also be used to modify the units of derived quantities.

Table 1.2: Standard prefixes.

Factor	Prefix	Symbol	Factor	Prefix	Symbol
$10^{18}$	exa-	E	$10^{-1}$	deci-	d
$10^{15}$	peta-	P	$10^{-2}$	centi-	c
$10^{12}$	tera-	T	$10^{-3}$	milli-	m
$10^{9}$	giga-	G	$10^{-6}$	micro-	$\mu$
$10^{6}$	mega-	M	$10^{-9}$	nano-	n
$10^{3}$	kilo-	k	$10^{-12}$	pico-	p
$10^{2}$	hecto-	h	$10^{-15}$	femto-	f
$10^{1}$	deka-	da	$10^{-18}$	atto-	a