General Science


  • Line of pale dust thrown up by meteorite impact, observed on the surface of the Moon and Mercury, leading back to the crater whose creation produced the ray. Ray craters are thought to be the youngest on the Moon, some as recent as a few hundred million years.



  • A straight line drawn from the origin of a diagram. In the Heckscher-Ohlin Model, two rays are used to define a diversification cone.


  • A line of radiant energy, such as light, whose cross section is very small. Also, a representation of such a line. For example, the path of a single photon.
  • A particle or beam of particles emitted or radiated from a source. For instance, alpha rays, beta rays, cathode rays, or gamma rays.
  • A particle or beam of particles whose cross section is small or very small. For example, that utilized in electron beam lithography.
  • One of multiple lines diverging from a single point. For example, radii from a circle. Also called half-line.


  • noun a line of light, radiation or heat

Origin & History of “ray”

Ray the ‘beam of light or energy’ (14th c.) and ray the fish-name (14th c.) are two different words. The former comes from rai, the Old French descendant of Latin radius ‘spoke of a wheel, ray’ (source also of English radiant, radio, radius, etc). The textile term rayon was coined from it in the early 1920s. Ray the fish-name comes via Old French raie from Latin raia, a word of unknown origin.