A regular pentagon has five lines of symmetry. An irregular pentagon, with non-equal side lengths and internal angles, may or may not have any lines of symmetry.
A line of symmetry is a line in a two-dimensional shape where the remnants on both sides are exact mirrored versions of each other. A line of symmetry in a regular pentagon must go from the center of any side to the vertex directly opposite to it. Because a regular pentagon has five sides, it also has five lines of symmetry. Most regular polygons have a number of lines of symmetry that are equal to the number of its sides.