表示时间关系的介词 from , since , for ,during
1：笼统的表示一段时间，要用 for ，如 for three years , for two months ,for ever .
eg:
He travelled in the desert for six months .
他在沙漠中旅行了6个月。
He has worked here for a year .
他已经在这里工作了一年。
2：如果要更具体表示一段时间，即要指明从何时到何时，那就得用 from...to /till/until.
eg:
Most people work from nine to /till six.
大多数人从上午9点工作到下午6点。
They played bridge from six to /till midnight .
他们打桥牌从6点打到半夜才停止。
3：如果只讲起点时间，不提终点时间，便用 since ,如 since Monday, since her arrival.
eg:
He has been here since Monday.
他从星期一就一直待在这里。
He wondered where Ann was .He had not seen her since their quarrel.
他不知安到何处去了。自从他俩争吵过，他就没有看见过他。
4：如果要表示具体的一段时间，还可用 during ,如 during the summer (of that year ), during 2015, during the Middle Ages（在中世纪），during my holidays（在我度假期间）,during his childhood .
eg:
He was ill for a week, and during that week he ate nothing .
他病了一星期，在那一星期中他没有吃东西。
He stayed in Shanghai from June to August ,and during that period he did a lot of reading .
6月至8月他待在上海，在那段时间他读了很多书。
以上两例都说明，用during 可表示一个整段时间；但用 during 也可表示某个时段中的某个时点。
eg:
It rained all Monday,but stopped raining during the night .
星期一一整天下午，但是夜里雨停了。
在这里，during the night 显然是星期一夜里某个时间雨停了。
表示已过的一段时间，during 和 for 意义相仿，可以交替使用。
eg:
We stayed in Shanghai during /for the remaining days of the summer vocation .
在暑假剩下的日子里，我们待在上海。
但是，如果表示“目的”，即表示要在尚未到来的一段时间做什么事情，那就只能用 for,而不能用 during .
eg:
I went there for my holidays .
我到那里去度假。
I rented a house on Lushan Mountain for the summer .
我在庐山上租了一幢房子以便在那里度夏。
