Ray (geometry).

Ray (geometry). Ray (geometry), portion of a line limited at one end by a point but extending to infinity in the other direction. A laser beam is similar to a ray: It has a definite beginning point (the laser) but no endpoint (the light continues forever unless something gets in the way). Rays are often designated according to their endpoints and a point through which they pass; a ray with endpoint A that passes through point B may be denoted Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved. .