I'd like to know what word to use to talk about a quadrilateral that has no distinctive feature (so, to express it's not a square, not a rectangle, nor rhombus, nor kite, nor parallelogram, nor trapezium/trapezoid.).

For triangles, for instance, the word "scalene" is right. Is it correct for quadrilaterals too?

2 Answers 2



I guess a Trapezium would be your answer as explained here.

But do notice that the definition of a Trapezium and that of a Trapezoid are swapped over in US and UK English usage as explained here.

  • Now, to avoid any possible confusion between trapezoid and trapezium, maybe I should use "irregular quadrilateral"?
    – zezollo
    Commented May 5, 2016 at 14:36
  • @zezollo Yes, as per the linked article, “general irregular quadrilateral” fits best. By the way, your description includes its distinctive features. Just because it's not something, doesn't mean it's not something else.
    – user3395
    Commented May 5, 2016 at 15:29
  • @zezollo : You can if you wish or you can use either of them according to the version of English used in your country.
    – 7_R3X
    Commented May 5, 2016 at 15:49
  • I need something that could be read without ambiguation, whenever possible, in any english-speaking country. Otherwise I'll default to british english I think, but it's an arbitrary choice. Many thanks for the link to mathopenref.com, it's exactly what I need to find the vocabulary I'm missing!
    – zezollo
    Commented May 5, 2016 at 17:20

Possibly, scalene means sides of unequal length, which (actually) can be a distinctive feature for a shape, e.g. scalene versus equilateral.

You may need to define what you mean by distinctive.

Quadrilateral is the generic term for a polygon with four sides.
But what determine "distinctive"? Right angles? Equal sides? Convexity?

A four sided shape with unequal sides would be best described as a quadrilateral or polygon.

  • Well, as there may be a lot of possible distinctions (right angles; angles equal by pairs; two or four parallel sides; 2, 3 or 4 equal sides etc.), I will add that it should mean any quadrilateral not being a square, nor rhombus, nor rectangle, nor kite, nor parallelogram, nor trapezium/trapezoid.
    – zezollo
    Commented May 5, 2016 at 14:34
  • Inconvenient of "quadrilateral": it does not exclude the "special" ones (like squares etc.).
    – zezollo
    Commented May 5, 2016 at 16:57
  • The main problem is that quadrilaterals have been around for a long time and are very useful, and so a specialised vocabulary has already been developed for them.
    – Peter
    Commented May 5, 2016 at 18:19

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