1. a big headache令人头痛的事情
2. a fraction of 一部分
3. a matter of concern 焦点
4. a series of 一系列,一连串above all 首先,尤其是
5. absent from不在,缺席
6. abundant in富于
7. account for 解释
8. accuse sb. of sth.控告
9. add to增加（add up to）
10. after all 毕竟,究竟
11. agree with同意
12. ahead of time / schedule提前
13. ahead of 在...之前（ahead of time 提前）
14. alien to与...相反
15. all at once 突然,同时
16. all but 几乎;除了...都
17. all of a sudden 突然
18. all over again 再一次,重新
19. all over 遍及
20. all right 令人满意的;可以
21. all the same 仍然,照样的
22. all the time 一直,始终
23. angry with sb. at/about sth.生气,愤怒
24. anxious about/for忧虑,担心
25. anything but 根本不
26. apart from 除...外(有/无)
27. appeal to 吸引，申诉，请求
28. applicable to适用于
29. apply to适用
30. appropriate for/to适当,合适
31. approximate to近似,接近
32. apt at聪明,善于
33. apt to易于
34. around the clock夜以继日
35. as a matter of fact 实际上
36. as a result(of) 因此,由于
37. as a rule 通常,照例
38. as far as ...be concerned 就...而言
39. as far as 远至,到...程度
40. as follows 如下
41. as for 至于,关于
42. as good as 和...几乎一样
43. as if 好像,防腐
44. as regards 关于,至于
45. as to 至于,关于
46. as usual 像平常一样,照例
47. as well as 除...外(也),即...又
48. as well 同样,也,还
49. ashamed of羞愧,害臊
50. aside from 除...外(还有)
51. ask for the moon异想天开
52. at a loss 茫然,不知所措
53. at a time 一次,每次
54. at all costs 不惜一切代价
55. at all events 不管怎样,无论如何