\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.

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.

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.

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.

{Axis of symmetry}. (Geom.) See under {Axis}.

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