Parallelogon
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A parallelogon is a convex polygon such that images of the polygon under translations only tile the plane when fitted together along entire sides.[1]
A parallelogon must have an even number of sides and opposite sides must be equal in length and parallel (hence the name). A less obvious restriction is that a parallelogon can only have four or six sides;[1] a four-sided parallelogon is a parallelogram. A regular octagon, for example, is not a parallelogon because it does not tile the plane.