symmetry

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun A relationship in which there is correspondence or similarity between entities or parts.
• noun Beauty as a result of pleasing proportions or harmonious arrangement.
• noun Physics Invariance under transformation. For example, a system that is invariant under rotation has rotational symmetry.

from The Century Dictionary.

• noun Proportionality; commensurability; the due proportion of parts; especially, the proper commensurability of the parts of the human body, according to a canon; hence, congruity; beauty of form.
• noun The metrical correspondence of parts with reference to a median plane, each element of geometrical form having its counterpart upon the opposite side of that plane, in the same continued perpendicular to the plane, and at the same distance from it, so that the two halves are geometrically related as a body and its image in a plane mirror: so, usually, in geometry.
• noun The composition of like and equably distributed parts to form a unitary whole; a balance between different parts, otherwise than in reference to a medial plane: but the mere repetition of parts, as in a pattern, is not properly called symmetry.
• noun Consistency; congruity; keeping; proper subordination of a part to the whole.
• noun In biology: In botany, specifically, agreement in number of parts among the cycles of organs which compose a flower. See symmetrical, 3.
• noun In zoölogy and anatomy, the symmetrical disposition or reversed repetition of parts around an axis or on opposite sides of any plane of the body.
• noun In moderu crystallography crystals are not only referred to certain systems (see crystallography) according to the relative lengths and inclinations of their assumed axes, but they are also further divided into classes, or groups, according to the kind and number of symmetry elements they possess.
• noun In Radial series, the Major Symmetry is built up by radial divisions of the first kind, producing segments whose adjacent parts are homologous, and related to each other as images.

from the GNU version of the Collaborative International Dictionary of English.

• noun A due proportion of the several parts of a body to each other; adaptation of the form or dimensions of the several parts of a thing to each other; the union and conformity of the members of a work to the whole.
• noun (Biol.) The law of likeness; similarity of structure; regularity in form and arrangement; orderly and similar distribution of parts, such that an animal may be divided into parts which are structurally symmetrical.
• noun Equality in the number of parts of the successive circles in a flower.
• noun Likeness in the form and size of floral organs of the same kind; regularity.
• noun (Geom.) See under Axis.
• noun that disposition of parts in which only the opposite sides are equal to each other.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Exact correspondence on either side of a dividing line, plane, center or axis.
• noun uncountable The satisfying arrangement of a balanced distribution of the elements of a whole.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (physics) the property of being isotropic; having the same value when measured in different directions
• noun (mathematics) an attribute of a shape or relation; exact reflection of form on opposite sides of a dividing line or plane
• noun balance among the parts of something