Fractional Units

units comprising a definite portion (fraction) of an established unit of physical values. With the establishment of the metric system, two principles were adopted for the formation of fractional units from reference units of the metric system: (a) the formation of denominations of fractional units by means of a prefix (deci-, centi-, mili-, and so on) and (b) decimalization in the ratio between the fractional unit and the original unit.

The prefixes adopted in the International System of Units for the formation of fractional units are given in Table 1.

Table 1. Fractional units
	Designation
	Prefix	Russian	International
10^-1 ................	deci-	∂	d
10^-2 ................	centi-	c	c
10^-3 ................	milli-	M	m
10^-6 ................	micro-	MK	μ
10^-9 ................	nano-	H	n
10^-12 ................	pico-	n	p
10^-15 ................	femto-	Φ	f
10^-18 ................	atto-	α	a