19. let sb alone to do 让…单独干…　　　 let alone 更不用说，何况　 He can’t walk, let alone run.　 let sb down 使…沮丧　　 let sb off 饶恕, 放过…　　 let out 放出；漏泄

18. Let that be a lesson to you.让那次成为你的教训。　 take/draw a lesson from 从…吸取教训　　　

17. in length　 在长度上　　　　　 at length = in detail　 详细的

16. legal 合法的　　 take legal action ， 　the legal age for driving

15. leave 离开　　 lock the door when you leave.　 leave sp 离开…　 leave for sp 离开去…　　　　　　 leave sb doing sth　 Please don't leave them waiting too long.　 leave the door open 让门开着　　　　

leave alone 让某人独自呆着，不干扰　 They left the poor child alone in the house all night.

leave behind 遗忘，留下，不带　　 He has left his umbrella left.　

leave out 省略　 You have left out a word in that sentence.

be on leave 度假　　　　 ask for leave　　 请假

14. learn　 学习　　 learn to do 　learn sth　 Never too old to learn.(谚)活到老，学到老。

　　　 　Learn of sth ,　 learn that… 　　　　learn from　

13. leak　 泄漏　 漏洞　　 The pipe has got a leak.　　　　 a gas leak 煤气泄漏　　　　　

12. league　　 联盟　　　　 a league number 团员　　　　 a league match 联赛

11. leaf though = look though　 翻阅　　　　 turn over a new leaf　 改过自新，重新开始

10. lead　 通向；领路　 lead sb by the arm 牵…的手　　 lead sb ( in ) doing 带领…做…　　　　

　　　　 lead/live a happy life 过幸福生活　 lead a miserable existence　 过着悲惨的生活　　

lead to 通向　 Hard work leads to success.