Points & Lines

Points, lines and planes are the building blocks of Geometry because they are necessary to define other geometric terms.  Knowing their description and notation is essential to gaining a thorough understanding of geometric shape.

A point has no width, length, height, or shape and specifies an exact location. Points are identified with a capital letter and are drawn as a dot. The figure below is called point P.

.P

A line can be thought of as a connected set of infinitely many points, therefore it extends forever in both directions. In Euclidean Geometry all lines are straight.  The name of a line passing through two different points A and D is referred to as line AD or line DA and can be denoted with a two-headed arrow over two points on the line. The arrows signify that the line drawn extends indefinitely in each direction.

Line AD

Points that lie on the same line are called collinear. For example, in the graph below, points P, Q, and R are collinear. Points Q, S and T are not.

Collinear

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