Why is a dilation not considered a rigid transformation?

A dilation is not considered a rigid transformation because it alters the size of a figure while maintaining its shape. Rigid transformations, such as translations, rotations, and reflections, preserve distances and angles, meaning the original figure and its image are congruent. In contrast, a dilation changes the dimensions of the figure, resulting in a similar figure that is either larger or smaller, but not congruent to the original. Thus, while the shape remains the same, the overall size does not, distinguishing dilations from rigid transformations.