A shape is an area that is separate from other shapes in the art work because of a distinct or implied boundary due to differences of value (light to dark, gray scale), colour (hue & temperature) or texture. (Art Fundamentals, Theory & Practice of Art, by Ocvirk et al) Shapes can be positive, i.e. figure, or negative, i.e. background. It is best to have only 3 to 5 major shapes in the work. Although there is a dominant value, temperature and hue in the shape, a shape should have a small amount of another of these elements. If a shape is primarily dark in value, you can use gradation to add a lighter value.
I sell my original paintings and fine art greeting cards at my Etsy internet shop. Fine art prints are sold at my Fine Art America shop. (See my above links.)
[Click on title of post to go to my Zazzle internet shop.]