Octagonal means having eight sides and eight angles.

The most familiar octagonal shape in everyday life is the stop sign. If you count its sides, you'll find exactly eight straight edges meeting at eight corners. This distinctive eight-sided shape makes stop signs instantly recognizable, even from a distance or when partially covered by snow.

Octagons appear in architecture too. The famous Dome of the Rock in Jerusalem has an octagonal floor plan, and many church towers, gazebos, and historic buildings use octagonal designs. Builders appreciate octagonal structures because they're nearly as efficient as circles for enclosing space, but much easier to construct with straight walls and flat materials.

In nature, octagonal shapes are rare, though you might spot them in certain crystals or snowflake formations. Mathematicians find octagons interesting because a regular octagon (where all sides and angles are equal) has each interior angle measuring exactly 135 degrees. If you tried tiling a floor with regular octagons, you'd discover they don't fit together perfectly without gaps, which is why you see them combined with squares in some tile patterns.