or by the type of transformation:

* An object has reflectional symmetry (line or mirror symmetry) if there is a line (or in 3D a plane) going through it which divides it into two pieces that are mirror images of each other.
*An object has rotational symmetry if the object can be rotated about a fixed point (or in 3D about a line) without changing the overall shape.
*An object has translational symmetry