symmetry

Definitions

1. 1.(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.
2. 2.(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.

Source: Webster's Unabridged Dictionary, 1913 edition (public domain, via GCIDE / Project Gutenberg).

Synonyms

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