angstrom, abbr. Å, unit of length equal to 10^-10 meter (0.0000000001 meter); it is used to measure the wavelengths of visible light and of other forms of electromagnetic radiation, such as ultraviolet radiation and X rays. Scientists now prefer to use the nanometer (nm); 1 nm=10 Å. The angstrom is named in honor of Swedish physicist Anders J. Ångström.