Jeans are not appropriate for a formal party.

正式聚会上穿牛仔裤不合适。

《牛津词典》

Appearing at such a formal party for the first time, I felt out of place and wanted to flee.

第一次出现在这样一个正式的聚会上，我感到很不自在，想要逃离。

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A school prom is a formal party to celebrate an important date at school, such as the end of high school or completing school exams.

学校舞会是一个正式的聚会，以庆祝学校的一个重要日子，如高中毕业或完成学校考试。

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However, Rodenberg says it is important remember that the state of New Jersey is not a formal party to this lawsuit.

FORBES: Department Of Justice Steps Into Fight Over Sports Gambling In New Jersey

Traditionally, a formal, summer garden-party dress did two things: it looked light and uplifting, while keeping all the bits one might generally expose to the sun covered.

WSJ: Fashion Meets Flora and Fauna

So civil servants have been dusting off their manuals on what to do in case of a hung parliament, and the Lib Dems elaborately refuse to set out the terms on which they would co-operate with either main party in a formal coalition or an informal alliance.

ECONOMIST: A briefing on the British election