Web Design, Web Development, Online Marketing, Web Solutions, SEO Company

About Us

You are here: About Us Metric

What does Exa mean?

Prefixes for decimal multiples Number Factor Name Symbol

Number	Factor	Name	Symbol
1000000000000000000000000	10 24	yotta	Y
1000000000000000000000	10 21	zetta	Z
1000000000000000000	10 18	exa	E
1000000000000000	10 15	peta	P
1000000000000	10 12	tera	T
1000000000	10 9	giga	G
1000000	10 6	mega	M
1000	10 3	kilo	k
100	10 2	hecto	h
10	10 1	deca	da
0.1	10 -1	deci	d
0.01	10 -2	centi	c
0.001	10 -3	milli	m
0.000001	10 -6	micro	µ
0.000000001	10 -9	nano	n
0.000000000001	10 -12	pico	p
0.000000000000001	10 -15	femto	f
0.000000000000000001	10 -18	atto	a
0.000000000000000000001	10 -21	zepto	z
0.000000000000000000000001	10 -24	yocto	y

Each prefix is represented by its own symbol. The symbols are case sensitive. Thus, m means milli and M means mega.

Prefixes ranging from micro to mega were first introduced in 1874 by BAAS as part of their CGS system. Later, 12 prefixes ranging from pico to tera were defined as part of the International System of Units - SI, which was adopted in 1960. SI is maintained by BIPM under exclusive supervision of CIPM and resolutions made by CGPM. Further 8 prefixes were added to SI in years 1964 (femto, atto), 1975 (peta, exa) and 1991 (zetta, zepto, yotta, yocto).

The prefixes have the following etymology:

exa	alteration of hexa from Greek hex meaning "six" (the sixth power of 103)
peta	alteration of penta from Greek pente meaning "five" (the fifth power of 103)
tera	from Greek teras meaning "monster"
giga	from Greek gigas meaning "giant"
mega	from Greek megas meaning "great"
kilo	from Greek khilioi meaning "thousand"
hecto	French, alteration of Greek hekaton meaning "hundred"
deca	from Greek deka meaning "ten"
deci	from Latin decimus meaning tenth, from decem meaning "ten"
centi	from Latin centi-, from centum meaning "hundred"
milli	from Latin mille meaning "thousand"
micro	from Greek mikros meaning "small"
nano	from Greek nannos meaning "dwarf"
pico	from Spanish pico meaning "small quantity"
femto	from Danish, or Norwegian word femten meaning "fifteen"
atto	from Danish, or Norwegian word atten meaning "eighteen"

The names zepto and zetta are derived from septo, from Latin septem which means seven (the seventh power of 103) and the letter 'z' is substituted for the letter 's' to avoid the duplicate use of the letter 's' as a symbol in SI. The names yocto and yotta are derived from Latin octo which means eight (the eighth power of 103); the letter 'y' is added to avoid the use of the letter 'o' as a symbol because it may be confused with the number zero. The CGPM has decided to name the prefixes, starting with the seventh power of 103, with the letters of the Latin alphabet, but starting from the end. Therefore the choice of letters 'z' and 'y'. The initial letter 'h' of the word hexa in standard French is silent, so it was removed in order to simplify things.