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. Its symbol is 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, pulsed lasers and some areas of electronics.

In 1 ns, light travels exactly 29.9792458 cm in a vacuum (via the definition of the metre). But the speed of light is slower in materials, indicated by an index of refraction greater than 1. Thus in air (1.003), light travels about 29.89 cm in 1 ns, but it travels only about 22.54 cm in water (1.33) each nanosecond.

See also

• 1 E-9 s for a list of times on the order of 1-10 nanoseconds