这些前置词（短语）均含有“在……前”之意。

before（之前） : 指空间位置或时间的“在……前”。表时间时，反义词为after；指空间位置时，其反义词是behind。

You should always wash your hands before meals.

饭前应该洗手。

Before leaving he said goodbye to each of them.

走前他和每个人都告了别。

She's always up before dawn.

她总是黎明前就起床了。

Before he could reach the door, she quickly closed it.

他还没走到门前她就迅速关上了门。

Before we make a decision, does anyone want to say anything else?

趁我们还未作决定，还有人想说什么吗？

She had to give the doorman a tip before he would help her with her suitcases (= he would not do it until she had given him a tip).

她得给看门人小费，好让他帮她提箱子。

in front of（前面） : 指在某地方之外的前面，即不在其中，多与静态动词连用，通常可与before通用。

She started talking to the man in front of her.

她开始跟前面的那个男人攀谈起来。

I stood for a few moments in front of the nearest shop window.

我在最近的一家商店的橱窗前站了一会儿。

They put a screen in front of me so I couldn't see what was going on.

他们在我面前竖了一面屏风，所以我看不到发生了什么事情。

We dried our clothes in front of the fire.

我们在火前烘干了衣服。

in the front of（前部） : 指在某地方之内的前面，即在其中的前部分。

The driver sits at the front of the bus.

驾驶员坐在公共汽车的前端。

Put the shortest flowers in the front (of the bunch).

把最短的花放在花束的靠前位置。

There is a table of contents in the front of a dictionary.

词典的开头有目录表。