数词
中文翻译：第
同义词：
['fifty-fifth', 'fifty-sixth']
例句：
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1. This is the 50th anniversary of our school's founding.
这是我们学校成立50周年。
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2. He was elected to the 55th National Congress of the Communist Party of China.
他被选为中国共产党第五十五次全国代表大会代表。
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3. The 56th edition of the book has just been published.
这本书的第56版刚刚出版。