1. at once [立刻；马上]
【构成】at[在] + once[一次]
【例句】Do it at once! [马上做！]
2. at last [最后；终于]
【构成】at[在] + last[最后的]
【例句】At last, he succeeded. [最后，他成功了。]
3. at first [起初；首先]
【构成】at[在] + first[第一；最初]
【例句】At first, I didn’t like him. [起初，我不喜欢他。]
4. at present [目前；现在]
【构成】at[在] + present[现在的；礼物]
【例句】I’m busy at present. [我现在很忙。]
5. at home [在家]
【构成】at[在] + home[家]
【例句】She is at home. [她在家。]
6. at school [在学校]
【构成】at[在] + school[学校]
【例句】The children are at school. [孩子们在学校。]
7. at work [在工作；上班]
【构成】at[在] + work[工作]
【例句】He is at work. [他在上班。]
8. at least [至少]
【构成】at[在] + least[最少]
【例句】You should sleep at least 8 hours a day. [你每天至少应该睡 8 小时。]
9. at most [至多；不超过]
【构成】at[在] + most[最多]
【例句】There are at most 50 people in the room. [房间里至多有 50 人。]
10. at night [在晚上]
【构成】at[在] + night[夜晚]
【例句】I often read books at night. [我经常在晚上读书。]
11. at noon [在中午]
【构成】at[在] + noon[中午]
【例句】We have lunch at noon. [我们在中午吃午饭。]
12. at the moment [此刻；当时]
【构成】at[在] + the[定冠词] + moment[时刻]
【例句】I’m not free at the moment. [我此刻没空。]
13. at the same time [同时]
【构成】at[在] + the[定冠词] + same[相同的] + time[时间]
【例句】They arrived at the same time. [他们同时到达。]
14. at times [有时；偶尔]
【构成】at[在] + times[时代；次数]
【例句】He is very busy, but at times he can relax. [他很忙，但有时他也能放松一下。]
15. at a loss [不知所措；困惑]
【构成】at[在] + a[一个] + loss[损失；迷失]
【例句】I’m at a loss what to do. [我不知道该怎么办。]
16. at any rate [无论如何；不管怎样]
【构成】at[在] + any[任何] + rate[比率；速度]
【例句】At any rate, we must finish the work on time. [无论如何，我们必须按时完成工作。]
17. at all costs [不惜一切代价]
【构成】at[在] + all[所有] + costs[代价]
【例句】We must win at all costs. [我们必须不惜一切代价取胜。]
18. at the age of [在…岁时]
【构成】at[在] + the[定冠词] + age[年龄] + of[的]
【例句】He started learning English at the age of five. [他五岁时开始学英语。]
19. at the end of [在…尽头；在…结束时]
【构成】at[在] + the[定冠词] + end[结尾；结束] + of[的]
【例句】There is a shop at the end of the street. [在街道的尽头有一家商店。]
20. at intervals [不时；每隔…时间（或距离）]
【构成】at[在] + intervals[间隔；间距]
【例句】The bells rang at intervals. [钟声不时地响起。]