How it works
This polygon graphic organizer builds the names one row at a time. Counting the sides and the angles of each shape shows that the two numbers always match.
Read the full guide
Where the names come from
Most polygon names join a Greek number prefix to -gon, as in pentagon and decagon. Three names break the pattern: triangle, quadrilateral and nonagon. Past 12 sides, mathematicians mostly write the number instead, as in 17-gon.
Polygon graphic organizers by grade
In the Common Core standards, 2nd grade students identify triangles, quadrilaterals, pentagons and hexagons, the first four rows of the chart. For a class that stops there, fold the page under the hexagon row.
- Heptagon is also called septagon, and nonagon is also called enneagon. Accept either.
- Ask for one sketch with unequal sides. A hexagon does not have to look like a cell of a honeycomb.
Questions and answers
What are the names of polygons by number of sides?
Triangle 3, quadrilateral 4, pentagon 5, hexagon 6, heptagon 7, octagon 8, nonagon 9 and decagon 10. After those come the hendecagon, with 11 sides, and the dodecagon, with 12.
What is a regular polygon?
A polygon whose sides are all the same length and whose angles are all the same size. Both must be true: equal sides alone, or equal angles alone, do not make a polygon regular.
Is a circle a polygon?
No. A polygon is a closed figure made only of straight line segments, and a circle is a curve. A figure with a gap in it is not a polygon either, because the segments must close.
How do you find the sum of the interior angles of a polygon?
Subtract 2 from the number of sides and multiply by 180°. A pentagon has 5 sides, so its interior angles add up to 3 × 180°, which is 540°. The 3 is the number of triangles the pentagon splits into.