In geometry, a line is a perfectly straight onedimensional figure extending infinitely in both directions. There are two subsets, or subcategories, of lines in geometry: line segments and rays.
Line Segments

A line segment is a piece of a line that has two distinct endpoints. Because of these endpoints, unlike a line, a line segment doesn't extend infinitely. Rather, it is finite, with a measurable length.
Rays

A ray is essentially a hybrid between a line and a line segment. A ray has exactly one endpoint  called its origin  and extends infinitely in the other direction. Like lines, rays are infinite and therefore immeasurable. Rays may sometimes be referred to as halflines.
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