Translation guide
A prom is a formal dance, usually for high school students, especially in the US. In Japan, there is no direct equivalent, so you need to describe it or use the loanword.
Referring to the prom as a school dance event
The loanword 'prom' is widely understood among younger Japanese people familiar with American culture. Use this in casual conversation.
来週のプロム、楽しみだね。
I'm looking forward to the prom next week.
A descriptive phrase meaning 'graduation dance party'. It clarifies the nature of the event for those unfamiliar with the term 'prom'.
アメリカの高校では、卒業ダンスパーティーが大きなイベントです。
In American high schools, the prom is a big event.
A simpler description: 'high school dance party'. Good for explaining to someone who doesn't know the term.
高校のダンスパーティーに何を着ていくかまだ決めてない。
I haven't decided what to wear to the prom yet.
Talking about attending the prom
The most natural way to say 'go to prom' using the loanword.
今年はプロムに行くつもり？
Are you planning to go to prom this year?
More formal: 'participate in the graduation dance party'.
多くの生徒が卒業ダンスパーティーに参加します。
Many students attend the prom.
Referring to the person you go to prom with
Means 'prom partner/date'. '相手' is a common word for partner in such contexts.
プロムの相手はもう決めた？
Have you decided on your prom date yet?
Uses the English loanword 'partner'. Also common.
彼はプロムのパートナーを探している。
He is looking for a prom date.
Talking about what to wear to prom
Specifically a prom dress. 'ドレス' implies a formal gown.
このプロムのドレス、どう思う？
What do you think of this prom dress?
More general: 'clothes for prom'. Can include suits, etc.
プロムの服を買いに行かないと。
I have to go buy an outfit for prom.
Since prom is not a Japanese tradition, you may need to briefly explain what it is when talking to someone unfamiliar with American school events. You can say: 「アメリカの高校で行われる、卒業前のフォーマルなダンスパーティーのことです。」 (It's a formal dance party held before graduation at American high schools.)