previously

1. ADV 先前；以前
   Previously means at some time before the period that you are talking about.
   1. Guyana's railways were previously owned by private companies...
      圭亚那的铁路以前是归私有企业所有的。
   2. The contract was awarded to a previously unknown company...
      合同签给了一个之前并不知名的公司。
   3. Previously she had very little time to work in her own garden.
      以前，她没什么时间打理自己的花园。
2. ADV （一段时间）以前
   You can use previously to say how much earlier one event was than another event.
   1. He had first entered the House 12 years previously...
      12年前，他首次成为议员。
   2. She had rented the flat from the council some fourteen months previously.
      大约14个月以前，她从地方政府那里租下了这套公寓。

If you are talking about a period measured back from some earlier time, you use before or previously. He had died a month before…She had rented the flat some fourteen months previously. You only use ago when you are talking about a period of time measured back from the present. You use for to say how long a period lasts in the past, present, or future, or how much time passes without something happening. She slept for eight hours… He will be away for three weeks… I hadn't seen him for four years. You use since to say when a period of time started. She has been with the group since it began. …the first civilian president since the coup 17 years ago. You also use since to refer to the last time that something happened, or to how much time passes without something happening. She hadn't eaten since breakfast… It was a long time since she had been to church.
如果谈论过去某个时间以前的时间，用 before 或者 previously：He had died a month before（他一个月前去世了），She had rented the flat some fourteen months previously（她大约14个月以前租下了这套公寓）。ago仅用于谈论现在之前的某段时间。for用来表示过去、现在或将来持续的一段时间或者某事多长时间没有发生，如：She slept for eight hours（她睡了8个小时），He will be away for three weeks（他会离开3个星期），I hadn't seen him for four years（我已经有4年没有见过他了）。since用来表示某段时间的开始，如：She has been with the group since it began（自从该集团创立起她就一直在其中工作），the first civilian president since the coup 17 years ago（自从17年前发生政变以来的第一位平民总统），since也可以用来某事最后一次发生的时间或者某事多长时间没有发生，如：She hadn't eaten since breakfast（她早餐以后就没吃过东西），It was a long time since she had been to church（她好久没去过教堂了）。

1. Spassky had never previously lost to his antagonist.
   斯帕斯基以往从未输给过他的对手。
2. The two fighters had previously boxed a 12-round match.
   这两位拳击手之前已经打了一场12回合的比赛。
3. The document was previously circulated in New York at the United Nations
   这份文件先前在纽约的联合国总部传阅过。
4. He may suddenly take a dislike to foods that he's previously enjoyed.
   对以前爱吃的食物，他兴许突然就没了胃口。
5. Reviews are distilled from articles previously published in the main column
   述评是从先前刊登在主要专栏的文章中提炼出来的。
6. The changed outlook entails higher economic growth than was previously assumed
   观念的改变势必会使得经济增长高于之前预计的水平。
7. A previously unknown extremist group has said it carried out Friday's bomb attack.
   一个先前不为人知的极端组织声称实施了星期五的炸弹袭击。
8. The evidence given in court was inconsistent with what he had previously told them.
   法庭上的证词与他当初告诉他们的不一致。
9. These black models are moving in on what was previously white territory: the lucrative cosmetic contracts.
   黑人模特正逐步涉足曾是白人主宰的领地：签约获利丰厚的化妆品行业。
10. Guyana's railways were previously owned by private companies
    圭亚那的铁路以前是归私有企业所有的。
11. The contract was awarded to a previously unknown company
    合同签给了一个之前并不知名的公司。
12. Previously she had very little time to work in her own garden.
    以前，她没什么时间打理自己的花园。
13. He had first entered the House 12 years previously
    12年前，他首次成为议员。
14. She had rented the flat from the council some fourteen months previously.
    大约14个月以前，她从地方政府那里租下了这套公寓。
15. It was previously a small monastery but the authorities turned all the monks out.
    那里原先是座小寺庙，但当局把所有僧侣都撵走了。
16. Radiation may damage cells in a way that was previously unforeseen
    辐射可能以一种我们过去未能预见到的方式破坏细胞。
17. We print a selection of previously unseen photos from the Spanish rider's early years.
    我们选了这位西班牙骑手早年一些不为人知的照片刊登出来。
18. Previously our mountain area [ region] is poor and impoverised.
    先前咱们山区很穷。
19. He certainly got a good break when he began to work in that firm; yet he deserved it because previously he had got a series of bad breaks.
    他开始在那家公司工作，一定交上了好运，他也应该这样，因为此前他遇上了一连串厄运。
20. Now it is time to associate the macro you created previously with this control.
    现在是时候将您前面创建的宏和这个控件关联起来了。
21. Previously, we said that all of the data in the system is stored in a tree.
    前面我们说系统中的所有数据都存储在一个树中。
22. Previously we had just passed the remainder of the list each time.
    以前我们每次只是传递了列表的剩余部分。
23. If you have previously added resource monitoring data sources to this schedule, you can Edit or Remove them.
    如果您先前已经将资源监控数据源添加到该进度表中，那么您可以Edit或Remove它们。
24. Install HACMP if it is has not previously been installed on all the nodes.
    如果还没有在所有节点上安装HACMP，现在就安装它。
25. This has already been hinted at previously when discussing method, tools, enablement, and organization.
    在讨论方法，工具，启动以及公司时，前文已经提到了这一点。
26. We discussed the built-in action previously.
    我们先前讨论了内置操作。
27. This means that we have to set all the previously mentioned properties.
    这意味着我们必须设置所有以前提到过的属性。
28. This assumes that the index has not been advised previously.
    这里是假设该索引之前还没有被建议。
29. Previously this was an informational file that you could query.
    以前，数据库历史文件是一种信息文件，您可以对其进行查询。

  ago before formerly previously【导航词义：以前】

  ago adv. 以前

〔辨析〕指从现在起往前推算一段时间，通常和一般过去时的动词连用。

  before adv. 先前，以前

〔辨析〕指过去某时间之前的时间或泛指以前，通常与动词的现在完成时连用，有时也可与动词的过去完成时或一般过去时连用，也可用于具体的一段时间；在间接引语中用 before 而不用 ago。

  formerly adv. 以前，从前

〔辨析〕泛指以前，有时常用于对比。

  previously adv. 以前，先前

〔辨析〕与 before 用法相同，但更加正式。

adv

1. at an earlier time or formerly
   1. she had previously lived in Chicago
   2. he was previously president of a bank
   3. better than anything previously proposed
   4. a previously unquestioned attitude
   5. antecedently arranged

   Synonym:    antecedently