annul
词根词缀：
annul v. 取消
an 加强 + nul〔= null〕没有，无 → 变没有 → 取消
null adj. 无效的；等于零的
nullification n. 无效；废弃
null 没有，无 + ification 形成… → 无效；废弃
nullify v. 取消；废除
null 没有，无 + ify 使… → 取消；废除
anaesthetic n. 麻醉剂
an 不，无 + aesthet 感觉 + ic 某种药 → 使无感觉的药 → 麻醉剂
anarchism n. 无政府主义
an 不，无 + arch 统治 + ism 表主义 → 无统治 → 无政府主义
anechoic adj. 无回声的
an 不，无 + echo 回声 + ic …的 → 无回声的
anesthesia n. 麻醉
an 不，无 + esthes〔= eshtet感觉〕+ ia 某种病 → 无感觉 → 麻醉
anharmonic adj. 不和谐的
an 不，无 + harmonic 和谐的 → 不和谐的
anonymous adj. 匿名的
an 不，无 + onym 名字 + ous …的 → 匿名的
annex v. 吞并
an 表加强 + nex〔= nect连接〕→ 连接到一起 → 吞并
annihilate v. 消灭
an 表加强 + nihil 无，零 + ate 使… → 成为零 → 消灭
annotate v. 注释
an 表加强 + not 标记 + ate 做 → 做标记 → 注释
announce v. 通告
an 表加强 + nounc 说 + e → 反复说 → 通告
annul v. 取消
an 表加强 + nul〔= null没有，无〕→ 变没有 → 取消
annunciate v. 宣告
an 表加强 + nunci 说 + ate 使… → 大声说 → 宣告
数据来源：新东方英语词汇速记大全
相关例句：
The courts later found grounds to annul the results, after the king urged them to sort out the mess.
在国王敦促法庭收拾烂摊子后，法庭随后宣布废除选举结果。
It can not fire women or unilaterally annul their labor contracts on the pretext of marriage, pregnancy, maternity leave or baby nursing.
不得以结婚、怀孕、产假、哺乳等为由，辞退女职工或单方面解除劳动合同；
I think allowing the wives of gay men to annul their marriages without providing support to their same-sex partners accordingly will squeeze us out, said Xiao Xiao, a 24-year-old gay man.
我认为允许男同性恋者的配偶取消他们的婚姻，没有为他们的同性伴侣提供相应的支持会把我们排斥出去，潇潇说，一位24岁的男同性恋者。
If you were a newlywed groom, you could annul a marriage if on your wedding night you discovered that your wife has bad breath.
如果你是新婚的新郎，你在新婚夜发现你的新娘有口臭你可以解除婚约。
To annul those administrative rules and regulations, decisions or orders of the State Council that contravene the Constitution or the law;
撤销国务院制定的同宪法、法律相抵触的行政法规、决定和命令；
To annul those local regulations or decisions of the organs of state power of provinces, autonomous regions, and municipalities directly under the Central Government that contravene the Constitution, the law or the administrative rules and regulations;
（八）撤销省、自治区、直辖市国家权力机关制定的同宪法、法律和行政法规相抵触的地方性法规和决议；