Which transformation is known to maintain the size but change the orientation of a shape?

The transformation that maintains the size of a shape while changing its orientation is reflection. When a shape is reflected over a line (also known as the line of reflection), it produces a mirror image of the original shape. The distances between corresponding points in the original shape and the reflected shape remain the same, which preserves the size. However, the orientation is altered; for example, if the shape is oriented one way in the original position, it will appear "flipped" in the reflected position.

In contrast, translation moves a shape without changing its orientation or size, while rotation changes the position of a shape by turning it around a point but maintains both its size and orientation. Dilation, on the other hand, changes the size of a shape while keeping its shape and orientation but does not preserve the original size. Therefore, reflection is unique among the transformations listed for its ability to change orientation without altering size.