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（尤指特定阶层的）礼仪，礼节;（尤指特定行业的）行为规范，规矩
Etiquette is a set of customs and rules for polite behaviour, especially among a particular class of people or in a particular profession.
例句
This was such a great breach of etiquette, he hardly knew what to do.
这是严重失礼的行为，他几乎手足无措。
...the rules of diplomatic etiquette.
外交礼节的规则