ETYM Latin symmetria, Greek; syn with, together + metron a measure: cf. French symétrie. Related to Syn-, and Meter rhythm.
Exact likeness in shape about a given line (axis), point, or plane. A figure has symmetry if one half can be rotated and/or reflected onto the other. (Symmetry preserves length, angle, but not necessarily orientation.) In a wider sense, symmetry exits if a change in the system leaves the essential features of the system unchanged; for example, reversing the sign of electric charges does not change the electrical behavior of an arrangement of charges.
1. Balance among the parts of something; SYN. proportion.
2. (Mathematics) An attribute of a shape; exact correspondence of form on opposite sides of a dividing line or plane; SYN. symmetricalness, correspondence, balance.