Nanometre
The nanometre (symbol: nm) is a unit used to measure length in the metric system. It is equal to one billionth of a metre () and for kilometre, it is equal to one trillionth of a kilometre (1 km / 1,000,000,000,000). The name combines the SI prefix nano- (from the Ancient Greek , , "dwarf") with the parent unit name metre (from Greek , , "unit of measurement"). It can be written in scientific notation as 1×10−9 m.