(also x-ray or X ray)Translate X-ray | into French | into German | into Italian | into Spanish
- 1an electromagnetic wave of high energy and very short wavelength, which is able to pass through many materials opaque to light.
- X-rays were formerly defined in terms of their wavelength, radiation of shorter wavelength than theirs being classed as gamma rays. They are now usually defined in terms of the mode of production: X-rays are produced by the deceleration of charged particles, especially electrons, or by electron transitions in atoms, while gamma rays arise from the radioactive decay of atomic nuclei
translation of German X-Strahlen (plural), from X- (because, when discovered in 1895, the nature of the rays was unknown) + Strahl 'ray'