主题是一个字符字符串，层次结构的每一层都以某种形式分界（通常使用正斜杠），例如 stocks/IBM。

A topic is a character string with each level in the hierarchy delimited in some fashion (often by a slash), for example, stocks/IBM.

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定界符：一个字符或者字符串，用来确定字符分割时候的分界。

A character or string used to indicate where a string should be split.

youdao