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The Collaborative International Dictionary of English v.0.48 (gcide)

Symmetry \Sym"me*try\, n. [L. symmetria, Gr. ?; sy`n with,
together ? a measure: cf. F. sym['e]trie. See {Syn-}, and
{Meter} rhythm.]
1. 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.
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2. (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.
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Note: Bilateral symmetry, or two-sidedness, in vertebrates,
etc., is that in which the body can be divided into
symmetrical halves by a vertical plane passing through
the middle; radial symmetry, as in echinoderms, is that
in which the individual parts are arranged
symmetrically around a central axis; serial symmetry,
or zonal symmetry, as in earthworms, is that in which
the segments or metameres of the body are disposed in a
zonal manner one after the other in a longitudinal
axis. This last is sometimes called metamerism.
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3. (Bot.)
(a) Equality in the number of parts of the successive
circles in a flower.
(b) Likeness in the form and size of floral organs of the
same kind; regularity.
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{Axis of symmetry}. (Geom.) See under {Axis}.

{Respective symmetry}, that disposition of parts in which
only the opposite sides are equal to each other.
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