> In geometry, how many sides does a trapezoid have?And the answer: four.Photo credit: Historic Bridges[https://historicbridges.org/bridges/browser/photos.php?bridgebrowser=truss/sarnia/&gallerynum=1&gallerysize=1].A trapezoid has four straight sides, but its exact shape depends on where youare in the world. For example, in the United States, a trapezoid has two sidesthat are parallel to each other, but in the United Kingdom, the word "trapezoid"refers to a 4-sided shape that doesn't have any parallel sides. The classification of trapezoids is uniquely contested. Outside of the U.S. andCanada, a quadrilateral with at least one pair of parallel sides is called atrapezium, but the shape known by that name within the U.S. and Canada isdefined as one with no parallel sides. Confused? Us too. Euclid, the forefather of modern geometry, defines a square as having equalsides and right angles; an oblong to have four right angles (but not four equalsides); a rhombus to have four equal sides (but no right angles); and a rhomboidto have equal opposite sides and equal opposite angles (but without right anglesand without four equal sides). All other quadrilaterals were classified astrapezia. Should be easy enough, right? Wrong. Interestingly, according to the Oxford English Dictionary, the confusionof trapezium and trapezoid between the U.S. and U.K. dates back to an error inHutton's Mathematical Dictionary in 1795, which directly reversed the acceptedmeanings. Hutton assigned trapezium to "no sides parallel" and trapezoid to "twosides parallel."In the United States, the Hutton definitions became standard, while the Proclusdefinitions remained standard in England. Two hundred years later, thecontroversy remains. Country by country, region by region, and even school byschool, the definitions of trapezoid and trapezium are often swapped.And now, a geometry joke:What do you call more than one L? The answer: A parallel!