1. The correspondence of the form and arrangement of elements or parts on opposite sides of a dividing line or plane or about a center or an axis:the symmetry of a butterfly's wings.

2. A relationship in which there is correspondence or similarity between entities or parts:the symmetry of the play, which opens and ends with a speech by a female character.

3. Beauty as a result of pleasing proportions or harmonious arrangement:"Here were the ringlets, framing a face of exquisite symmetry"(Clive Barker).

4. Physics Invariance under transformation. For example, a system that is invariant under rotation has rotational symmetry.