a basic body plan in which the left and right sides of the organism can be divided into approximate mirror images of each other along the midline.
bi erasureRead more in this article about some frequently asked questions and fun facts related to our definitions.
Does bimonthly mean twice a month or every two months?The prefix bi- usually means ‘every two’, so bimonthly means ‘every two months’.Semi- means ‘half’ or ‘halfway’, so semimonthly means ‘every two weeks’. However, bimonthly can also mean ‘twice a month’ – but it is rarely used that way. It is best to remember that bi- is “every two” and semi- is “halfway.”
Compare radial symmetry.
Origin of bilateral symmetry
First recorded in 1850–55
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Symmetrical arrangement, as of an organism or a body part, along a central axis, so that the body is divided into equivalent right and left halves by only one plane.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Symmetrical arrangement of an organism or part of an organism along a central axis, so that the organism or part can be divided into two equal halves. Bilateral symmetry is a characteristic of animals that are capable of moving freely through their environments. Compare radial symmetry.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.