What is a reflection?

A reflection is a transformation that flips a shape over a line, called the mirror line, to make a mirror image. Every point moves to the opposite side of the line but stays the same distance from it, and the shape keeps its size.

Examples

• Your face in a mirror is a reflection.
• Reflecting the letter b over a vertical line gives d.
• A shape and its reflection are congruent (same size and shape).

Quick facts

• A reflection keeps the shape the same size, just flipped.
• Reflection is closely linked to line symmetry.