Definition: A binary relation R for which a R b implies b R a.

See also reflexive, transitive, antisymmetric.

Note: The relation "not equal to" is symmetric: if a ≠ b, then b ≠ a. However, "loves" is not symmetric since love might not be reciprocated. The relation "is married to" is symmetric, but not antisymmetric: if Paul is married to Marlena, then Marlena is married to Paul (symmetric), but that does not mean that Paul and Marlena are the same person.

Author: PEB

Go to the Dictionary of Algorithms and Data Structures home page.

If you have suggestions, corrections, or comments, please get in touch with Paul Black.

Entry modified 17 December 2004.
HTML page formatted Wed Mar 13 12:42:46 2019.

Cite this as:
Paul E. Black, "symmetric", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 17 December 2004. (accessed TODAY) Available from: