Rhombus vs. Rhomboid

Date: 08/27/2002 at 00:38:18
From: Emma Stewart
Subject: Geometry

On a recent version of Australia's "Who wants to be a Millionaire?" 
they asked: What shape is the diamond in a set of playing cards?
a) rhomboid b) trapezoid c) trapezium d) rhombus.

I have worked out that the answer is a rhombus. What is a rhomboid? Is 
it just the adjective from rhombus or is it a shape?

Date: 08/27/2002 at 09:06:31
From: Doctor Sarah
Subject: Re: Geometry

Hi Emma - thanks for writing to Dr. Math.

See Eric Weisstein's MathWorld:

   Rhombus
     http://mathworld.wolfram.com/Rhombus.html 

   "A quadrilateral with both pairs of opposite sides 
    parallel and all sides the same length, i.e., 
    an equilateral parallelogram."

   Rhomboid
     http://mathworld.wolfram.com/Rhomboid.html 

   "A parallelogram in which angles are oblique and 
    adjacent sides are of unequal length." 

- Doctor Sarah, The Math Forum
  http://mathforum.org/dr.math/