Answer:

The word isometry means equal measure. An isometry is a transformation in which the distance between any two points is unchanged by the transformation. The effect is to map any shape onto an identical shape.

Rotations, reflections and translations are isometries, but enlargements are not because they alter lengths. Isometries which do not alter sense are called direct isometries. Rotations and translations are direct isometries. Isometries which alter sense are called opposite isometries. Reflections and glide reflections are opposite isometries.