Nanometer (nm)
Definition: A nanometer (symbol: nm) is one billionth of a meter (0.000000001 m or 10^-9 m). It is a metric unit used for extremely small lengths.
History/origin: The nanometer emerged from scientific use of the metric system as researchers needed practical names for very small scales. It became especially common in physics, chemistry, optics, and semiconductor manufacturing.
Current use: Nanometers are widely used to describe wavelengths of light, dimensions of molecules, atomic-scale structures, and fabrication sizes in electronics and materials science.
