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A big open-air building where the seats rise in rows around a central space, so that everyone can look down and see. The ancient Roman ones were oval and had no roof — the Colosseum in Rome is the most famous — and crowds sat there to watch fights and shows.
A big open-air building where the seats rise in rows around a central space一座露天的大型建築，座位一排排圍著中央的空間往上升 so that everyone can look down and see這樣每個人都能往下看清楚。 The ancient Roman ones were oval and had no roof古羅馬的amphitheatre是橢圓形、沒有屋頂 the Colosseum in Rome is the most famous最有名的就是羅馬的競技場 and crowds sat there to watch fights and shows群眾坐在那裡看格鬥和表演。
Today the word is used three ways. It still names those ancient ruins. It also names modern outdoor places built in the same shape for concerts and plays. And it is used loosely for any bowl-shaped hollow in the land, or any steep lecture room where the seats climb up in curved rows, even indoors and even with a roof — so the 'without a roof' part of the dictionary answer is true of the Roman ones but not always of the modern ones.
Today the word is used three ways現在這個字有三種用法。 It still names those ancient ruins它仍然可以指那些古代遺跡。 It also names modern outdoor places built in the same shape for concerts and plays也可以指用同樣形狀蓋來辦演唱會、戲劇的現代戶外場地。 And it is used loosely for any bowl-shaped hollow in the land也會比較鬆散地用來指任何碗狀的天然地形 or any steep lecture room where the seats climb up in curved rows或是座位呈弧形往上排的陡峭講堂 even indoors and even with a roof就算是在室內、有屋頂也一樣 so the 'without a roof' part of the dictionary answer is true of the Roman ones but not always of the modern ones所以字典說'沒有屋頂'只對古羅馬的那種成立，現代的不一定。
British spelling is 'amphitheatre'; American spelling is 'amphitheater'.
British spelling is 'amphitheatre'; American spelling is 'amphitheater'英式拼法是'amphitheatre'，美式拼法是'amphitheater'。
Both are correct; just be consistent.
Both are correct; just be consistent兩種都對，只要前後一致就好。
原始詞典資料3 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。
Amphitheatrename
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A town in the Shire of Pyrenees, central western Victoria, Australia
amphitheatrenoun/ˈæmfɪˌθiːətə/
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An open, outdoor theatre (which may be a theatre in the round, or have a stage with seating on only one side), especially one from the classical period of ancient Greece or Rome, or a modern venue of similar design.
- Ancient Roman amphitheatres were mostly oval or circular in plan, with seating tiers that surrounded the central performance area, like a modern open-air stadium.
- We had previously visited the building prepared for the assemblage, which was a vast pentagonal semicircular amphitheatre of painted wood and canvas work, ...
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geographygeologynatural-sciencesA natural formation of a similar shape, where a steep mountain or slope or particular rock formation forms a partial or complete bowl, especially one used as a performance space (and possibly modified by carving out seats, etc) because the slopes naturally amplify or echo sound.
- The difference between the approach to Baylen from the west and from the east, is that on the former side the traveller reaches the town through a semicircular amphitheatre of upland, while by the latter he comes up a V-shaped valley ...
- Brecon or Aberhonddu, a typical Welsh town of 5,350 inhabitants, stands in a grand amphitheatre of hills and mountains at the confluence of the rivers Usk, Honddu, and Tarell.
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。