What divides something in half so that each half is a mirror image of each other?

A line of symmetry divides a shape or object into two equal parts, creating mirror images of each side. This line can be vertical, horizontal, or diagonal, depending on the shape. In geometric figures, such as circles or rectangles, this symmetrical division ensures that each half is identical in shape and size. Examples include the vertical line through the center of a butterfly or the horizontal line through the middle of a heart.