1) absent from 指“不在”某处按常理可以预计会在的地方，而且这个“不在”造成一定的后果。因此，如果是临时离开一下，不用 absent from。

• I called on him unexpectedly but he was out（或 not in，不说 absent）.我临时去拜访他，但他不在家。
• He has never been absent from school.他从来不缺课。

也就是说，absent from 通常用于主语按常理与 from 后面的地点有固定联系的情况（因而 absent from 这个地点就多少显得有点不平常），否则就不自然，例如不应说某儿童 absent from 某老人院。表示本来以为某地有某物，结果发现并没有，也可以用 absent from，以表示认识上的一个变化，

• We can see why whole groups of organisms... should be absent from oceanic islands, whilst the most isolated islands possess their own peculiar species of aerial mammals or bats.(Charles Darwin, The Origin of Species)我们可以看到，为什么整批的有机体…在海岛上看不到，而那些最为隔绝的岛屿，却有自己独特的空中哺乳动物亦即蝙蝠的品种。

2) absent in 可以有两个截然相反的含义，一个是“在某地不存在”，或“不在某地”，另一个则是“不在通常所在地而在某地”。如何判别，方法比较简单。如果主语是人，in 后面是个表示地点的名词，该地点并非该人经常所在之处，那么 absent in 就是“不在通常所在之处而在某地”。

• Mr. Allworthy had been absent a full quarter of a year in London...按照小说故事，Allworthy 经常住在 Somersetshire，不在 London (Henry Fielding, The History of Tom Jones, a Foundling) 阿尔沃西先生原先离开此地到伦敦去了整整一个季度…
• ... there were some of the legatees whose place of abode was unknown, or even whose persons were not known, or who were absent in a remote country, so that it was not possible (for the executor of a testament) to acquaint them (William Strahan, The Civil Law in Its Natural Order, p.551)…有些遗产承受人居住地址不明，甚至身份也不明，或者不在此地而身处远方，因而（遗嘱执行人）无法通知他们。
• Much of his trade was with France, and his son was born while he was absent in that country.他的生意很大部分是同法国进行的，他儿子也是当他离家在法国时出生的。
• In the fourteenth year of the reign of King Henry the Third, he was made captain-general of the king's forces in Brittany, and, whilst absent in that country, a war broke out in Ireland, whereupon he was sent to that kingdom with a considerable army to restore tranquility. (The History of the Knights Templars: The Temple Church: Chapter XII, p.336)在亨利第三在位的第十四年，他被任命为国王驻布列塔尼部队的总兵，而正当他不在国内而在布列塔尼的时候，爱尔兰爆发了战争，他就被指派率领一支大军到那个王国去恢复秩序。
• ... he has become financial adviser to Romania. He was absent in that country during the period of my stay in France.…他成了罗马尼亚的财政顾问。我在法国期间他不在法国而在罗马尼亚。

但是，如果主语不是人而是物，或者是抽象事物，或者 in 后面的名词不是指明确的地点而是其他事物，则 absent in 就是“在…并不存在”的意思。

• Snow is absent in some countries.有些国家终年无雪。
• Measles is virtually absent in these countries.麻疹在这些国家实际上已经绝了迹。
• Mutation is a sudden change in a gene which enables a child to inherit a characteristic totally absent in his or her parents.变异是一个基因发生的突然变化，它使得一个孩子获得一个他或她父母身上根本没有的特征。
• The recent paintings in this show, from 2003, introduce an element of color absent in his earlier work.这次展览中，2003 年以后的近期画作，引进了他早期作品中所没有的一种用色手法。

3) absent 是个形容词，但有时也可以当作介词使用放在已有限定词的名词前面，相当于 without，表示“在缺乏…的情况下”。

• Absent such a direct threat, Mr. Carter professes to feel no pressure. (William Safire, The New York Times, Dec. 20, 1976)既然没有这样一个直接的威胁，卡特先生就装作不感到有什么压力了。
• Those strategies are being shaped absent any real knowledge of what Fitzgerald might do before the grand jury's scheduled dissolution on Oct. 28. (Times, Oct. 24, 2005)那些对策目前在形成过程中的时候，尚未确实知道菲兹杰拉尔德在大陪审团预定 10 月 28 日解散之前会有何行动。
• Absent any in-place protection against the missiles described here, "defense" means either a counteroffensive, nuclear retaliation or open-ended diplomacy, cease-fires and negotiation.既然对这里所描述的导弹没有什么当堂防御的办法，那么，所谓“防御”，要么是反攻、核报复，要么就是泛泛的外交交涉、停火和谈判。