Number & MeasureGreek → English
Heptagon
/ˈhɛptəɡɒn/noun
A plane figure with seven straight sides and seven angles.
The Greek roots
ἑπτά
heptá
seven
γωνία
gōnía
angle, corner
Literally: “seven angles”
The story of the word
Seven angles, and of all the small regular polygons this is the awkward one. It cannot be drawn with compass and straightedge alone: Gauss set out in 1796 the condition that decides which regular polygons can be, and seven fails it, with Pierre Wantzel completing the proof in 1837. Britain's fifty-pence piece sidesteps the geometry by curving its seven sides into a shape of constant width, so a slot machine measures it the same whichever way it goes in.
- How it travelled
- Ancient Greek → Latin → English
- First recorded
- 16th century
Same family
hexagonoctagonheptathlonpolygon
In a sentence
Draw a heptagon freehand and it always comes out looking apologetic.
The tower is a heptagon, which the builders must have regretted.