N-VAR
废除；取消；宣告无效
The annulment of a contract or marriage is an official declaration that it is invalid, so that legally it is considered never to have existed.
例句
...the annulment of the elections...
选举被宣告无效
He may appeal to the Pope for an annulment of his 24-year marriage.
他可能会请求主教宣告他那长达24年的婚姻无效。