✔ 最佳答案
annual dinner = 週年晚宴 (這就是最普通的講法)
anniversary dinner = 週年晚宴 (這就是第某某週年晚宴的講法, anniversary前要加the xxth or xxst or xxnd anniversary dinner depends on which year)
但亦有以餐舞會(ball)形式的週年晚宴來興祝的。於是有xxth anniversary dinner ball這玩意了。
當然,主辦人可再加上多些花款,但已是題外話了。
參考: my 40 years experience with foreigners