An Etymological Dictionary of Astronomy and Astrophysics

The → electromagnetic radiation with the longest → wavelengths (and lowest energies), ranging from 0.3 mm to several km. Radio waves form a very broad category, which includes the
→ submillimeter waves (with a wavelength of 0.3-1 mm) and → microwave regions (1 mm to several cm).

See also: → radio; → wave.