On the whole, topic-comment sentences, the main sentence type in Chinese, are led by topic and based on mainly a single-track system-meaning.

总体来说，主题句是主题统领下的、近乎语义单轨的结构，是汉语的主要句型。

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Considering all these differences in sentence structure, translators find switching subject-predicate into topic-comment sentences is often necessary but difficult in English-Chinese translation.

由于英汉语在句子结构上的巨大差异，英汉翻译中，句式转换通常是必要的但也是十分困难的一个环节。

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