Nanosecond
A nanosecond is an SI derived unit of time equal to 10-9 of a second.The word nanosecond is formed by the prefix nano and the unit second. It is abbreviated as ns.
It is only infrequently put into everyday use. In technical situations it is however a very common unit, especially in the line of telecommunications and some areas of electronics.
Light travels approximately 30 cm (exactly 29.9792458 cm) in 1 ns.
The definition of the SI unit metre is 1/299792458 of the distance light travels in one second, so the above is exact.
See also