<p><strong>Noun</strong></p><ul><li>A device that separates a beam of light into two ray beams, usually by means of reflection, and that brings the rays together to produce interference, used to measure wavelength, index of refraction, and astronomical distances (Optics).</li><li>An instrument for measuring the angular separation of double stars or the diameter of giant stars by means of the interference phenomena of light emitted by these stars (Astronomy).</li></ul>