Geometry Dictionary Assignments

Polygon Sorting Activity

Students will already be familiar with many, many shapes, but they may not know the mathematical names. One simple way to start is to identify whether or not a shape is a polygon. A polygon is closed figure made up of at least three sides and angles. Triangles, quadrilaterals, pentagons, hexagons, etc. are all polygons. Any shape with curves or open ends is NOT a polygon. Polygons can be weird shapes, have convex and concave sides, and can have any number of sides.

Have students move shapes from a template into the appropriate columns on their own storyboard. Interactive whiteboards or projected computer screens make this an engaging class activity, but students can just as easily work individually or in pairs on a computer.

See also Polygonia and Roundsville for a short math story.

Polygons can be categorized by the number of sides (and therefore angles) they have:

  • Three-sided polygons - triangles
  • Four-sided polygons - quadrilaterals
  • Five-sided polygons - pentagons
  • Six-sided polygons - hexagons
  • Seven-sided polygons - heptagons*
  • Eight-sided polygons - octagons
  • Nine-sided polygons - nonagons*
  • Ten-sided polygons - decagons*
  • Eleven-sided polygons - hendecagons*
  • Twelve-sided polygons - dodecagons*

*These shapes are not required by the Common Core, but it is nice to have the names handy if inquiring minds want to know.

Geometry terms and definitions

Home > By Subject > Geometry > Terms/ Definitions

To save you having to refer to a dictionary, we’ve listed below some of the more common geometry terms and geometry definitions to help you help with your child’s geometry homework.


Definition/ Description

PointA location in space - a dot on a piece of paper
LineConnects two points via the shortest path and continues indefinitely (forever) in both directions
Line SegmentPart of a line between two points
Perpendicular Line SegmentLine Segments that intersect (cross) at an angle of 90°

This Math Open Reference Project provides additional information with more geometry terms and definitions.


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