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A shape is the form of an object or its external boundary, outline, or external surface, as opposed to other properties such as color, texture, or material composition.

An example of the different definitions of shape. The two triangles on the left are congruent, while the third is similar to them. The last triangle is neither similar nor congruent to any of the others, but it is homeomorphic.

A shape is the form of an object or its external boundary, outline, or external surface, as opposed to other properties such as color, texture, or material composition.

Psychologists have theorized that humans mentally break down images into simple geometric shapes called geons. Examples of geons include cones and spheres.