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A nanosecond (ns) is one billionth of a second (10−9 or 1/1,000,000,000 s). One nanosecond is to one second as one second is to 31.7 years.
The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns.
A nanosecond is equal to 1000 picoseconds or 1⁄1000 microsecond. Because the next SI unit is 1000 times larger, times of 10−8 and 10−7 seconds are typically expressed as tens or hundreds of nanoseconds.
Times of this magnitude are commonly encountered in telecommunications, pulsed lasers and some areas of electronics. Some notable measurements in this range include:
Common measurements 
- 0.5 nanoseconds (0.5 ns) - the average life of a molecule of positronium hydride.
- 1.0 nanosecond (1.0 ns) – cycle time for radio frequency 1 GHz (1×109 hertz), an inverse unit. This corresponds to a radio wavelength of 1 light-nanosecond or 0.3 m, as can be calculated by multiplying 1 ns by the speed of light (approximately 3×108 m/s) to determine the distance traveled.
- 1.0 nanosecond (1.0 ns) – cycle time for a 1 GHz processor. Common processors today have frequencies around 1-3.5 GHz, so the cycle time is somewhat shorter than a nanosecond.
- 1.017 nanoseconds (approximately) – time taken for light to travel 1 foot in a vacuum.
- 3.33564095 nanoseconds (approximately) – time taken for light to travel 1 metre in a vacuum. (In air or water light travels more slowly; see index of refraction)
- 10 nanoseconds – one "shake", ( as in a "shake of a lamb's tail") approximate time of one generation of a nuclear chain reaction with fast neutrons
- 10 nanoseconds (10 ns) – cycle time for frequency 100 megahertz (1×108 Hertz), radio wavelength 3 m (VHF, FM band)
- 12 nanoseconds – half-life of a K meson
- 20–40 nanoseconds – time of fusion reaction in a hydrogen bomb
- 77 nanoseconds – a sixth (a 60th of a 60th of a 60th of a 60th of a second)
- 100 nanoseconds – cycle time for frequency 10 MHz, radio wavelength 30 m (shortwave)
- 333 nanoseconds – cycle time of highest medium wave radio frequency, 3 MHz
- 500 nanoseconds – T1 time of Josephson phase qubit (see also Qubit) as of May 2005
- 6×1010 nanoseconds - one minute
See also