zepto- [ZEP toh]
(Latin: septo-, seven; a decimal prefix [10-21] used in the international metric system for measurements)
This prefix is used in the metric [decimal] system as sextillionth [U.S.] or quadrillionth part [U.K.], 10-21 [0.000 000 000 000 000 000 001]. The metric symbol is z.
zeptomole (zmol)
One zmol equals approximately 600 atoms or molecules.
zeptosecond (zs, zsec)
One sextillionth (10-21) of a second.
zeptowatt (zW)
The sextillionth [U.S.] or quadrillionth part [U.K.], 10-21 [0.000 000 000 000 000 000 001] of a watt or the approximate power of Galileo space probe's radio signal (when at Jupiter) as received on earth by a 70 meter DSN antenna, or the Deep Space Network, which is an international network of communication facilities that supports interplanetary spacecraft missions.
Related "metric" families:
yotta;
zetta;
exa;
peta;
tera;
giga;
mega;
kilo;
hecto;
deka;
deci;
centi;
milli;
micro;
nano;
pico;
femto;
atto;
yocto.
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