M5S2U2 - Geometry (2D figures)

• Side


  A line segment on the boundary (an edge).

  
• Angle


  A figure formed by two rays with a common endpoint.

  
• Vertex (vertices - plural)

  The point of intersection for two sides of a plane figure.

  
• Congruent


  Having the same size and shape.

  
• Polygon


  A closed figure formed by three or more line segments.

  
• Regular polygon


  A polygon with equal angles and equal sides.

  
• Right triangle


  A triangle that has a 90 degree angle.

  
• Acute triangle


  A triangle that contains only angles that are less than 90 degrees.

  
• Obtuse triangle


  A triangle with one angle that is greater than 90 degrees.

  
• Equilateral triangle


  A triangle with three congruent (same) sides.

  
• Isosceles triangle


  A triangle that has 2 congruent (equal) sides.
• Scalene triangle


  A triangle with no congruent (equal) sides.
• Quadrilateral


  A polygon with four sides

  
• Rectangle


  A quadrilateral with four right angles

  
• Square


  A quadrilateral with 4 sides that are equal and has all 90 degree angles.

  
• Parallelogram


  A quadrilateral with two pairs of parallel sides

  
• Rhombus


  A parallelogram with four congruent (equal) sides.
• Kite


  A quadrilateral with two pairs of adjacent sides congruent and no opposite sides congruent.

  
• Trapezoid


  A quadrilateral with exactly one pair of parallel sides.

  
• Pentagon


  A polygon with 5 sides.

  
• Hexagon


  A polygon with 6 sides.

  
• Heptagon


  A polygon with 7 sides.

  
• Octagon


  A polygon with 8 sides.

  
• Nonagon


  A polygon with 9 sides.

  
• Decagon


  A polygon with 10 sides.

  
• Two-dimensional figure (2D)


  A flat figure. Example: polygon.

  
• Attribute / property


  A quality or characteristic used to describe something.