Explore Parallelogram on MathWorld

A parallelogram is a quadrilateral with opposite sides parallel and therefore opposite angles equal.

Parallelogram is an elementary-school-level concept. It is listed in the California State Standards for Grade 3.


Rectangle: A rectangle is a quadrilateral with opposite sides of equal length and with four right angles.
Square: A square is a polygon with four sides of equal length and at right angles to each other.


Angle: An angle is a measure of the amount of rotation about the point of intersection of two lines or line segments that is required to bring one into correspondence with the other.
Parallel: In two-dimensional Euclidean space, two lines that do not intersect are said to be parallel. In three-dimensional Euclidean space, parallel lines not only fail to intersect, but also maintain a constant separation between points closest to each other on the two lines.
Polygon: A polygon is a two-dimensional figure that consists of a collection of line segments, joined at their ends.

Classroom Articles on Polygons

  • Decagon
  • Octagon
  • Dodecagon
  • Pentagon
  • Equilateral Triangle
  • Quadrilateral
  • Hendecagon
  • Regular Polygon
  • Heptagon
  • Right Triangle
  • Hexagon
  • Trapezoid
  • Isosceles Triangle
  • Triangle
  • Nonagon

  • Classroom Articles on Geometry (Up to Elementary-School Level)

  • Acute Angle
  • Perimeter
  • Area
  • Perpendicular
  • Circle
  • Point
  • Cone
  • Prism
  • Cube
  • Pyramid
  • Cylinder
  • Radius
  • Diameter
  • Sphere
  • Geometric Construction
  • Surface Area
  • Obtuse Angle
  • Volume