Nanometre
The nanometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth of a metre ( 0.000000001 m) . The name combines the SI prefix nano- (from the Ancient Greek νάνος, nanos, "dwarf") with the parent unit name metre (from Greek μέτρον, metrοn, "unit of measurement"). It can be written in scientific notation as 1×10 m, in engineering notation as 1 E−9 m, and is simply 1/1 000 000 000 m. One nanometre equals ten ångströms.