A Euclidean line is a flat, infinitely large one-dimensional space following the laws of Euclidean geometry. It is often mistaken for a line segment, which is a connected subset of the line of finite length with two points as its boundary. A line can be used to bisect a polygon; any linear cross section of a polygon will be a line segment. The way the length of this line segment changes can give information about the structure of the polygon. Polygons can also have lines of symmetry through which they can be reflected.