舞会(wǔ huì) - dance, ball, dance party in Mandarin

舞会 (wǔ huì) is an organised dance: a school dance, a ballroom evening, a formal ball. The 会 ending marks it as a scheduled event rather than an activity, exactly as it does in 音乐会 (concert), 运动会 (sports day) and 展览会 (exhibition).

Keep it apart from 跳舞, which is the verb, the act of dancing. 我喜欢跳舞 is "I like dancing"; 我喜欢舞会 is "I like balls" as occasions. And a modern night out with loud music is usually 派对 or 蹦迪, not 舞会, which sounds a shade formal and old-fashioned, closer to "ball" than to "party".

You go to one with 参加 (to attend) or 去, and you dance at one with 在舞会上跳舞. The 上 is compulsory there: a Mandarin event is a surface you are on, not a place you are in.