马同鞋，您有点让俺眼晕的说~~~

什么“看比赛垫在屁股底下”“生火取暖”的？
这两个词的最大区别在于
use - employment (使用-从动词来的) or usefulness（有用性）
usage - 强调customary practice，习惯和惯例，尤其指词语的惯用法.

体会sentences blow:
1. English grammar and usage 英语语法和惯用法，不能用use

2. This book describes the principles of word usage. 单词的用法，不能用use

3. He is critized for his frequent use of wrong words。“使用”错误的词，强调employment,用use, 不能用usage

4.The usage of bright colors can greatly enhance the feeling of warmth in a room（X）错，应是the use of color 强调的是color的使用, 不能用usage

5.Drug use among teens has beenabigproblem，用use，而不是usage，用药（吸毒）这一行为

这是这两词最主要的区别，keep this in mind，use is a general word while usage is more specific.

另usage还有the manner of using things (treatment)的意思
This machine has been damaged by rough usage.不经心使用而损坏了

Hope this is helpful to you ~~