Points, Line, and Planes

• Undefined Terms do not have a formal definition in geometry.
• Point: Has no dimension. Represented by a dot.
• Line: Has one dimension. Represented by a line with two arrowheads, but it extends without end.
• Plane: Has two dimensions. Represented by a shape that looks like a floor, but it extends without end.
• Collinear Points: Lie on the same line.
• Coplanar Points: Lie in the same plane.
• Defined Terms can be described using known words such as point or line.
• Line Segment: Consist of two endpoints and all points on the line between those two points.
• Ray: Consists of one endpoint and all the points in one direction on its line.
• Opposite Rays: Rays beginning at the same endpoint, but going in opposite directions on the line.
• Ways to write a Line Segment:

  Segment AB, Segment BA
• Two or more geometric figures intersect if they have one or more points in common.
• The intersection of a figure is the set of points they have in common.
• Circumference: The distance around the boundary of a circle.
• Perimeter: The distance around a polygon.
• Area: The number of square units covered by a figure.
• Ways to write a Point:

  Point A, Point B, Point C
• Ways to write a Line:

  Line l, Line AB, Line BA
• Ways to write a Plane:

  Plane M, Plane ABC