Which transformation changes the size of a figure but not its shape?

The transformation that changes the size of a figure but not its shape is dilation. Dilation involves scaling a figure uniformly in all directions from a fixed point (the center of dilation), which adjusts the size of the figure while preserving its shape. This means that every point on the figure moves away from or towards the center by a certain scale factor, resulting in a larger or smaller version of the original figure without distorting its angles or proportions.

Other transformations, such as reflection, rotation, and translation, do not change the size of the figure at all. Reflection flips the figure over a line, rotation turns it around a point, and translation shifts it from one position to another without altering its dimensions. Therefore, dilation is unique in that it specifically modifies the size while keeping the shape unchanged.