Definition:Diameter of Quadrilateral

Let $$ABCD$$ be a quadrilateral:


 * DiameterOfQuadrilateral.png

The diameters of $$ABCD$$ are the lines $$AC$$ and $$BD$$ joining their opposite vertices.

Compare with
Note the difference between this definition and that of the diameter of a general geometric figure.

In the latter, the diameter is specifically the longest dimension of the figure.

Also known as
The diameters of a quadrilateral are also commonly known as its diagonals.