# Homotopy Type Theory relation > history (changes)

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## Definition

A relation over a type family $A$ indexed by a type $I$ is a predicate $R$ over the dependent product? type

$\prod_{i:I} A(i)$

A binary relation over types $A$ and $B$ is a predicate $\mapsto$ over the product type $A \times B$.

## See also

Last revised on June 15, 2022 at 22:36:24. See the history of this page for a list of all contributions to it.