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    Lines, Rays & Line Segments

    A line is defined as a straight curve.  Often, arrowheads are present on the ends of lines to represent continuation in both directions indefintely.

    Any two points on a line may be used to denote it as a line.  Symbolically, this is expressed by an overbar with arrowheads at each end over two letters corresponding to points on the line.  Consequently, any of the following notations represent the line above:

    The notations above are read as "Line AB," "Line BA," "Line AC," and so forth.

    A ray is occasionally referred to as a half line.  Rays begin at one point and continue indefinitely in a single direction after passing through another point (reference illustration below):


    Similar to the methodology described above, a single arrowhead overbar is used to denote a ray.  Accordingly, the ray above may be denoted as:

    The notations above are read as "Ray DE" and "Ray DF" respectively.  The first letter represents the endpoint while the second letter represents another point on the ray.

    A line segment is the portion of a line between two points (reference depiction below):

    Line segments are represented by a single overbar with no arrowheads over the letters representing the two endpoints.  Consequently, the line segment above may be represented by either:

    The notations above are read as "Line Segment GH" and "Line Segment HG" respectively.

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