<span>This could be something like art conventions. So while you might have art from several different areas, they use similar techniques because these represent the conventions of the art itself. For example, you could have artists from two different countries in Europe that speak different languages, etc but they both use the same conventions of the impressionist style because that's inherent in the particular style of art.</span>
Freeform shapes can be closed or open, and have no defined name or qualities. Geometric shapes are close shapes, with a specific name and distinct qualities.
