free-study 是自由作业 self-study 是自学 independent study是独立学习 study by oneself in scheduled time 自习 The course for you to study by yourself in scheduled time 自习课 study hall自修室，自修课 Study hall 在很多课程表里面有作为自习课被用到
self study lesson.
self-study course independent study course
我来说一说，恩~《self-study》的意思是〈自习〉lesson是众所周知的〈课〉的意思，所以把这两个词连起来说或者,就是所谓的〈自习课〉。
free-study 个人见解 study by oneself in scheduled time这个是自习的意思 是在字典上查的。不过我想用不到那么长吧。
答：individual study详情>>
答：10的n次方 ten to the nth power. 10的9次方 ten to the 9th power.详情>>
