Reciprocal Relationship
The reciprocal relationship of a relationship [latex]\mathcal{R}[/latex] of X in Y is the relationship of Y in X, such that, for all the elements of the domain of [latex]\mathcal{R}[/latex], if y = [latex]\mathcal{R}[/latex](x), then x = [latex]\mathcal{R}^{-1}[/latex](y).
