Geometric anomoly?
March 10, 2005 5:11 PM   Subscribe

Why is a rectangle not called a quadrangle?
posted by punkfloyd to Grab Bag (12 answers total)
 
"Quadrangle" is a general term for four-sided figures. Squares, rectangles, trapezoids, kites, etc are all quadrangles. Rectangles are called "rectangle" because it's more specific than "quadrangle".
posted by kenko at 5:16 PM on March 10, 2005


Because a quadrangle is not necessarily a rectangle.
posted by noius at 5:17 PM on March 10, 2005


First of all, it is, kind of: rectangle is a subset of quadrangle.

A "quadrangle" is a structure with 4 angles. Lots of things fit into this category, including rhombuses, trapezoids, etc.

A "rectangle" is structure with all right angles, that's what the "rect" part is for. I guess you could argue that it should more properly be called a "rectquadrangle" or something, but this is the word we've got. As you can see, there are lots of quadrangles that don't fit this definition.

Square is then a subset of rectangle, where all the sides are the same length.
posted by rkent at 5:20 PM on March 10, 2005


whoops, ignored the preview step... what those guys said.
posted by rkent at 5:20 PM on March 10, 2005


"Quadrangle" is a general term for four-sided figures

Strictly speaking, Quadrangle is a general term for four-angled figures. "Quadrilateral" is the general term for four-sided figures. Not sure if or how you could have a figure that was one and not the other, but if you did, you'd be mighty glad the correct distinguishing term was available.

In terms of regullar usage, though, quadrilateral is the one I always heard referring to any (usually non-rectangular) four-sided figure, while every "quadrangle" (e.g. on college campuses) I've ever encountered has been a rectangle.
posted by soyjoy at 6:20 PM on March 10, 2005


A "rectangle" is structure with all right angles, that's what the "rect" part is for. I guess you could argue that it should more properly be called a "rectquadrangle" or something,

nope, no need - all right angles necessitates four sides.
posted by mdn at 6:56 PM on March 10, 2005



posted by knave at 7:18 PM on March 10, 2005


doh.
posted by mdn at 7:35 PM on March 10, 2005


and tastefully color-coordinated!
posted by nebulawindphone at 9:39 PM on March 10, 2005


Is that 90' or 270'?
posted by AlexReynolds at 11:23 PM on March 10, 2005


Because rectilinear sounds cooler than quadralinear. Wait - no it doesn't... Because rectum... nevermind...
posted by raster at 6:50 AM on March 11, 2005


Obviously mdn meant convex euclidean planar shapes only, since there are also triangles with all right angles in elliptical geometry.
posted by techgnollogic at 2:30 AM on March 12, 2005


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