at last与at length区别

这一对短语都有“终于”、“最后”的意思,但涵义和使用场合有所不同.
At length 这个词组共有三个意义： （1）长时间地.例如：He spoke at（great）length．（2）详细地.例如：They treated the subject at length．（3）终于；最后.例：After flying for ten hours,they got to San Francisco at length．
作第三种意义使用时,at length与at last同义,但它们的内涵却有所不同.当人们做某事时,遇到了困难,经过奋斗,最后得以完成,在这种场合,我们用at last.如果在做的过程中,经历了很长的时间才得以完成,这时候,不论困难大小,都可用at length表示.为此,我们说,at last强调的是“经过努力奋斗”；at length 强调的是“经历很长的时间”.通过下列例句的对比,不难看出它们之间的区别：
Before they climbed down the side of the cliff,they met with many obstacles,but they surmounted them at last．
从悬崖的侧面爬下来之前,他们遇到了许多障碍,但终于把它们克服了.
In spite of every obstacle,they have at last arrived at the destination．
尽管障碍很多,他们终于到达了目的地.
After a voyage of five months,they at length arrived safe and sound．
经过五个月的航行,他们终于安全抵达.
请注意,用length构成的介词短语很多,常见的有：
* Exhibition Centre measures 200 metres in length．
香港展览中心长达二百公尺.
They discussed this problem at great length．
他们非常详细地讨论了这个问题.
Yesterday I had my picture taken at the studio at full length．
昨天我在照相馆拍了一张全身照.
They travelled through the length and breadth of the country．
他们走遍全国.