cre [5eikE] n. 英亩
(类)ream·paper=acre·land 纸的单位·纸=亩·土地
acquit [ E5kwit ] vt. 宣告无罪(to free or clear from a charge or accusation)
acrid [5AkrId] 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 [AkrI5mEJnIEs] 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 [ 5AkrEbAt ] 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 [ 5Aktjueit ] vt. 促使
(记)act行为+uate→使有作为→促使 参考：activate 刺激，使活泼
acuity [ E5kjuiti ] n. 锐利，视力或观察力敏锐;敏捷(acuteness of vision or perception; keenness)
acumen [E5kju:mEn] 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)
(反)acute ◆ mild 急性的 ◆ 温和的
(例)acute disease. 急性病
adage [5AdidV] n. 谚语(a saying often in metaphorical form that embodies a common observation)
(同)saying, word, proverb, saw 谚语, byword 格言，谚语，笑柄
(记)ad+age(时代)联想：谚语在不同时代都禁得起检验。易混淆：badge徽章
adamant [5AdEmEnt] adj. 坚硬的;固执的，不动摇的(unshakable especially in opposite)
(类)adamant·flexibility=refractory·control 坚固不柔软=难以操作的不可控制
impossible·execute=adamant·move 不可能的不可操作=顽固的不改变路线
(反)vacillatory 动摇 incline to yield 容易妥协的
(记)a+dam大坝+ant 一个大坝上的蚂蚁;如果不够固执和坚强，千里之堤，如何毁于蚁穴呢?
(例)He was adamant in his determination to punish the corrupt officials.
他下了决心，坚决惩治那些贪官污吏。
adapt [E5dApt] vt. 修改，使适应(to bring into correspondence or make suitable)
(反)adapt 修改 ◆ remain unchanged 保持不变的
(例)a species that has adapted well to winter climes. 很适应冬天气候的物种
(记)ad+apt(灵巧的，适当的;本身就是一个词啊)