1. factor sth. in：将……纳入，将……列为重要因素
It's necessary to factor the weather conditons in our plan.
将天气情况作为重要因素列入计划是很有必要的。
2. fade out：淡出
As the old man went far, the backgroud music faded out.
随着老人走远，背景音乐也渐歇。
替换短语：fade in：淡入
As the music turned louder, the sight of the man's back faded in.
随着音乐声变大，男人的背影也渐显。
3. fail in：在……上失败
You will fail in the entrance exam if you don't study.
如果你不读书，入学考试一定会失败的。
混淆短语：without fail：一定，必定
You will pass the entrance exam without fail as long as you study hard.
只要你用功读书，入学考试一定会通过的。
4. fall behind：落后
You will fall behind ohters if you don't study hard.
如果你不用功读书，就会落在别人后面。
混淆短语：behind the times：过时的，跟不上时代的
If you haven't heard of iPod, you are behind the times.
如果你没听过iPod，那你肯定跟不上时代。
5. fall in love with：爱上……
Mary fell in love with a gentleman.
玛丽爱上了一个绅士。
混淆短语：love to do sth.：喜欢做某事
I wonder why Mary loves to watch horror films.
我很想知道为什么玛丽喜欢看恐怖片。
6. fall short of：没有达到
I'm afraid that the result of your study is sitll fall shotr the our expectations.
恐怕你的学习成绩还没达到我们的期望。
混淆短语：go short of：缺乏
If it still doesn't rain, we will go short of water in a week.
如果再不下雨，我们不出一个星期就会缺水了。
7. familiar with：熟悉
I have only been here for a few days, I'm not quite familiar with the streets.
我来这里才几天，对这里的街道并不熟悉。
混淆短语：be on familiar terms with：与……交情好
The people here are on familiar terms with each other.
这里人彼此之间交情都很好。