(mathematics) an attribute of a shape or relation; exact reflection of form on opposite sides of a dividing line or plane
"The butterfly's wings displayed perfect symmetry, as the left side was an exact mirror image of the right across its central body."
balance among the parts of something
"The architect designed the building to have perfect symmetry, ensuring that every column and window was balanced on either side of the central axis."
Exact correspondence on either side of a dividing line, plane, center or axis.
"The butterfly's wings display perfect symmetry, mirroring each other exactly across its central body line."
In plain English: Symmetry is when both sides of something look exactly alike, as if you could fold it down the middle and they match perfectly.
"The butterfly's wings showed perfect symmetry, with both sides looking exactly alike."
Usage: Symmetry describes a balanced arrangement where one half mirrors the other across a central point or line. Use this term when referring to visual balance in objects like faces or buildings rather than abstract concepts such as fairness.
The word symmetry comes from the Latin symmetria, which was borrowed from Ancient Greek to describe things that are measured together or in proportion. It entered English through French and Italian during the Renaissance as a term for balanced arrangement rather than retaining its original technical sense of shared measurement.