Transformation of axes
The concept of reflection is introduced first although transformation of axes is not involved in it.
Pre-image: The original shape of an object is called the pre-image.
Reflection: A reflection is a kind of transformation which is a 'flip' of a shape over a line (or a point or a plane) of reflection. It is always the mirror image of an object i.e, with right and left reversed. An object and its reflection have the same shape and size, but the figures face in opposite directions. A reflection can be seen, for example, in water, in mirror, or in shiny surface. See adjacent figures.
Image: The reflection of an object (pre-image) is called the image of that object.
Line reflection: A reflection over a line is a transformation in which each point of the original figure has an image that is at the same distance from the line of reflection as the original point but on the opposite side of the line. When a figure is reflected over a line the image is congruent to its pre-image and this property is known as isometry.