A regular octagon has eight lines of symmetry.
To understand why, let’s first define what a line of symmetry is. A line of symmetry is an imaginary line that divides a shape into two identical parts, such that one side is a mirror reflection of the other. In the case of a regular octagon, which has eight equal sides and eight equal angles, you can draw a line through each vertex and the midpoint of the opposite side. This gives you four lines of symmetry. Additionally, if you draw a line connecting the midpoints of opposite sides, you get another four lines of symmetry. Therefore, all together, a regular octagon has eight distinct lines of symmetry.