An octagon has eight sides.
To understand why, let’s break it down: the prefix ‘octo-‘ comes from the Greek word for eight. So, when we refer to an octagon in geometry, we are talking about a polygon that is defined by eight straight sides and eight angles. A regular octagon has sides of equal length and angles of equal measure, typically seen in shapes like stop signs. Thus, the answer is clear—an octagon is characterized by its eight sides.