acre n. 英亩
(类)ream·paper=acre·land 纸的单位·纸=亩·土地
acquit vt. 宣告无罪(to free or clear from a charge or accusation)
acrid adj. 辛辣的，刺鼻的(sharp and harsh in taste or odor)
(类)acrid·odor=grating/ piercing·sound 刺激的·味道=刺耳的·声音(形修饰名)
acrid·gentleness=forthright·guile 辛辣的·温和的=直率的·狡诈(反面特征)
(反)acrid
◆ gentle 辛辣的
◆ 温和的
acrimonious adj. 刻薄的(caustic especially in feeling, language, or manner)
(反)acrimonious
◆ harmonious 刻薄的
◆ 和谐融洽的
(记)acri(尖，酸)→刻薄的
(例)His tendency to utter acrimonious remarks alienated his audience.
说话刻薄的习惯使他疏远了听众。
acrobat n.杂技演员, 随机应变者
(记)acro高+ bat走 →高空行走(如阿迪江)→杂技演员
参考：acrophobia恐高症acronym首字母缩写词
actuate vt. 促使
(记)act行为+uate→使有作为→促使 参考：activate 刺激，使活泼
acuity n. 锐利，视力或观察力敏锐;敏捷(acuteness of vision or perception; keenness)
acumen n.敏锐，聪明(keenness and depth of perception)
(类)alacrity·prompt=acumen·shrewd 敏捷·快速=敏锐·干练(同义)
(反)acumen
◆ unable to discerning 敏锐
◆ 不能辨别的
(记)acu(尖)+men →敏锐 参考：acupuncture 针灸
(例)His business acumen helped him to succeed where others had failed.
他在商业上的敏锐帮他在其他人失败的地方获得成功。
acute adj. 敏锐的，锐角的;(医)急性的(having a sudden onset 发作, sharp rise, and short course)
(类)perspicacity·acute=caprice·whimsical 敏锐·敏锐的=反复无常·多变的(名形同义)
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