Chapter 18 Two-Dimensional Shapes

  • Chapter 18

    Chapter Objective:

    * Polygons can be classified by the number of sides, corners and angles. Figures can be congruent or symmetrical, or both.


    plane figure - A plane figure is a flat figure. It can be open or closed.

    open figure - An open figure is a plane figure that does not start and end at the same point; the figure is 'open' and not closed.

    closed figure - A closed figure is a figure that starts and ends at the same point; the figure is 'closed' and not left open.

    polygon - A polygon is a closed plane figure that is formed with three or more line segments.

    vertex - A vertex is a point where two sides of a polygon meet.

    quadrilateral - A quadrilateral is a polygon that has four sides and four angles.

    parallel - Parallel refers to lines that will never meet, no matter how long they are drawn. The lines will always have the same distance between them. 

    rhombus - A rhombus is a parallelogram that has four sides of equal length.

    parallelogram - A parallelogram is a quadrilateral with two pairs of opposite sides that are parallel. Only the opposite sides of a parallelogram need to be equal in length.

    pentagon - A pentagon is a polygon that has five sides.

    octagon - An octagon is a polygon that has eight sides.

    tangram - A tangram is made up of seven polygons that can be put together to make a square.

    slide - When you slide a a figure, it can be slid in any direction to a new position. 

    flip - When you flip a figure, you turn a shape front to back over a line.