A zig-zag is a pattern made up of small corners at variable angles, though constant within the zig-zag, tracing a path between two parallel lines; it can be described as both jagged and fairly regular. From the point of view of symmetry, a regular zig-zag can be generated from a simple motif like a line segment by repeated application of a glide reflection. The origin of the word is unclear. Its first printed appearance was in French books in the late 17th century.