Nanometer Definition: Size & Applications Explained

A nanometer (nm) is a unit of length in the metric system, equal to one billionth of a meter (0.000000001 meters). It is commonly used to measure the size of atoms, molecules, and other very small objects. For example, the average diameter of a carbon atom is about 0.15 nanometers, and the width of a DNA molecule is about 2 nanometers.