同学你好，该知识点来自沪江网校《零基础直达BEC商务英语高级【职场精英随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好
在“写东西”的意义上，“write”、“write down”和“write up”有着很大区别，不能相互替换。
1.   “Write something”：意为写的动作，对应的是没写的概念。如：
a)      Molière wrote his last play, The Imaginary Invalid, in 1673.
b)      I'm planning to write my essay on Molière's comedies next week.

2.       “Write something down”或“write down something”：意为写下备忘，强调具体内容，不是很正式；对应的是默记的概念。如：
a)       I wrote down your number, but now I can't find it.
b)      You don't have to write everything down that the lecturer says.

3.    “Write something up”或“write up something”：意为完整清晰地记录，强调写作目标，相对正式；对应的是部分写完的概念。“Up”常用于强调完成，例如“chop up”就比“chop”彻底。如：
a)      I'm going to write up my lecture notes this evening.
b)      Write your notes up while they're still fresh.

祝学习愉快！