A mural is any piece of artwork painted or applied directly on a wall, ceiling or other permanent surface. A distinguishing characteristic of mural painting is that the architectural elements of the given space are harmoniously incorporated into the picture.
Some wall paintings are painted on large canvases, which are then attached to the wall (e.g., with marouflage). Whether these works can be accurately called "murals" is a subject of some controversy in the art world but the technique has been in common use since the late 19th century.