A nanosecond (ns) is an S.I. unit of time equal to one billionth of a second, that is, 1⁄1 000 000 000 of a second, or 10−9 seconds. The term combines the prefix nano- with the basic unit for one-sixtieth of a minute. A nanosecond is equal to 1000 picoseconds or 1⁄1000 microsecond.