Shapes by Their Sides

The number of straight sides gives a shape its name.

Any shape with 4 straight sides has a group name.

Quadrilateral is any shape with 4 straight sides.

A big family

Squares, rectangles, rhombuses, and trapezoids are all quadrilaterals.

Five and six

Five sides make a pentagon. Six sides make a hexagon.

Shapes are named by their sides

A triangle has 3 sides, a quadrilateral has 4, a pentagon has 5, and a hexagon has 6. The names come from old Greek and Latin counting words, which is why they sound unfamiliar. Count the sides and the name follows.

Same name, very different looks

A tall thin triangle and a wide flat one are both triangles, because both have three straight sides. A square, a rectangle, and a slanted four-sided shape are all quadrilaterals. Never judge a shape by whether it looks like the picture in the book.

Sides and corners always match

Every closed straight-sided shape has as many corners as sides. A pentagon has 5 sides and 5 corners. So you can count whichever is easier to see and get the same answer — a handy check when a shape is drawn awkwardly.