Ray
This is an old revision of this page, as edited by Foxtrot (talk | contribs) at 11:59, July 17, 2008. It may differ significantly from current revision.
A ray is a portion of a line which starts at a given point and continues endlessly in one direction. Intuitively, it can be thought of as "half" a line because it extends infinitely in only one direction rather than two, opposite directions as lines do. Of course, quantitatively, "half a line" is somewhat meaningless since a line is infinite and half of infinity is still infinity.