Definition: A binary relation R for which a R b and b R a implies a = b.
See also symmetric, irreflexive, partial order.
Note: The relation "less than or equal to" is antisymmetric: if a ≤ b and b ≤ a, then a=b. The relation "is married to" is symmetric, but not antisymmetric: if Paul is married to Marlena, then Marlena is married to Paul (symmetric), but Paul and Marlena are not the same person.
Equals (=) is antisymmetric because a = b and b = a implies a = b. Less than (<) is also antisymmetric because a < b and b < a is always false, and false implies anything.
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Entry modified 17 December 2004.
HTML page formatted Fri Mar 25 16:20:34 2011.
Cite this as:
Paul E. Black, "antisymmetric", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 17 December 2004. (accessed TODAY) Available from: http://www.nist.gov/dads/HTML/antisymmetric.html