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A heptagon is a flat shape with seven straight sides and seven corners. If all the sides are equal and all the corners match, it is a regular heptagon, the tidy figure in a maths book. If the sides are different, it is still a heptagon; it is just uneven. You will meet the word in geometry class much more than in the street. In real life people usually say a seven-sided shape. Though actually, a few coins, logos, and buildings use this shape, so you may see it without seeing the word. The hepta- piece means seven. A has six sides — hexa- is six — and that one-letter difference traps a lot of students.
七邊形
組成From Ancient Greek ἑπτάγωνον (heptágōnon), from ἑπτά (heptá, “seven”) + γωνία (gōnía, “angle”). By surface analysis: hepta- (seven) + -gon (angle, corner).
同家族的字
- hexagonsame -gon “angle”; hexa- is six, hepta- is seven
- pentagonsame -gon “angle”
- octagonsame -gon “angle”
- heptathlonsame hepta- “seven”
原始詞典資料1 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
heptagonnoun/ˈhɛp.tə.ɡɒn/
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A polygon with seven sides and seven angles.
- Meronyms: angle, side; see also Thesaurus:polygon
- So if Colorado is not a rectangle, what is it? Well, not a pentagon, (Greek for 5-sider), hexagon (6-sider), or a heptagon (7-sider), but a—hold on to something—hexahectaenneacontakaiheptagon (697-sider).
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。