 See also: Symmetry in biology
Symmetry is a property of certain geometrical objects that appears the same when mirrored or reflected along an axis. This axis has to cross the shape through the middle of that object dividing into equal halves.
The precise notions of symmetry have various measures and operational definitions. For example, symmetry may be observed
 with respect to the passage of time;
 as a spatial relationship;
 through transformations such as rotation;
 through other kinds of transformations;
 as an aspect of scientific models, language, music and even knowledge itself.
Asymmetry
Asymmetry is the absence of symmetry. It is best defined like that because symmetry is relatively rare, and all other objects are asymmetric.
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A fractallike shape that has reflectional symmetry, rotational symmetry and selfsimilarity, three forms of symmetry. This shape is obtained by a finite subdivision rule.

Seen from the side, the Taj Mahal has bilateral symmetry; from the top (in plan), it has fourfold symmetry.