Shape is defined as a two-dimensional area or mass delimited by contour lines. There are two main types of shapes: geometric shapes which follow mathematical patterns and transmit order, and organic shapes which have irregular profiles and suggest more dynamism. Shapes can also be open or closed, and positive or negative depending on whether they are completely enclosed by a line or define empty space. The key parts of a shape include the outline/contour, silhouette, and infill. Shapes are used in art to create the illusion of three-dimensional space and distance through varying techniques like size, overlapping, and contrasting colors.