What is it called when a figure can be mapped onto itself by reflecting it across a line?

When a figure can be mapped onto itself by reflecting it across a line, this property is known as line symmetry. This means that if you were to draw a line through the figure, one half of the figure would mirror the other half exactly.

In this context, line symmetry defines the relationship between the two halves of the figure regarding the line of reflection, where each point on one side of the line corresponds directly to a point on the opposite side at the same distance from the line. Figures with line symmetry, such as butterflies or certain geometric shapes, can be folded along this line, and the two halves will align perfectly.

Other types of symmetry include point symmetry, where rotation around a central point results in the same figure, and rotational symmetry, which involves rotating the figure around a center point to obtain a matching alignment of itself. Translational symmetry involves sliding a figure along a direction to match itself without any rotation or flipping involved. Each of these has its own definition and application, making line symmetry unique in the context of reflective properties of figures.