(definition)

**Definition:**
A *relation* between exactly two items at a time, such as "greater than" (>), "not equal to" (≠), "proper subset of" (⊂), or "is connected to" (has an *edge* to) for *vertices* of a *graph*.

**Generalization** (I am a kind of ...)

*relation*.

**Specialization** (... is a kind of me.)

*dictionary*.

**See also**
*binary function*, *reflexive*, *symmetric*, *transitive*, *antisymmetric*, *irreflexive*.

*Note:
One may think of a binary relation as a binary function whose range is {true, false}. For example since 3 > 2, GreaterThan(3, 2) = true.*

Author: PEB

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Entry modified 2 November 2020.

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Cite this as:

Paul E. Black, "binary relation", in
*Dictionary of Algorithms and Data Structures* [online], Paul E. Black, ed. 2 November 2020. (accessed TODAY)
Available from: https://www.nist.gov/dads/HTML/binaryRelation.html