In 'come back', 'break down' and 'fall off', 'back', 'down' and 'off' are all adverbial particles.

在come back、break down和fall off中，back、down和off都是副词小词。

《牛津词典》

Inflation could fall back into single figures as early as this month.

通货膨胀最早在本月就能回落到一位数。

《柯林斯英汉双解大词典》

He has her support to fall back on when the going gets tough.

当进展艰难时，他可以依赖她的支持。

《柯林斯英汉双解大词典》

An order came for him to fall back and support our right.

VOA: special.2010.03.27

Would the winner of the war slaughter the enemy that would fall behind or would they give them back?

战争胜利的一方会屠杀对方落在后面的人,还是任其溃逃

耶鲁公开课 - 古希腊历史简介课程节选

Well let's see. My fall back is, I could just do linear search, walk down the list one at a time, just comparing those things. OK. So that's sort of my base. But what if I wanted, you know, how do I want to get to that sorted list? All right?

我只能做线性搜索了,一次遍历一遍列表，一个一个比较，但如果我想要,那怎样得到有序的列表呢？,现在的一个问题是，我们排序之前？

麻省理工公开课 - 计算机科学及编程导论课程节选

Microsoft came out with a surprisingly good smartphone platform way back in fall 2010 -- in some ways, it was better than the iPhone from the moment it launched.

CNN: This is the year Microsoft fights back

He stood up well, didn't back away from it, but had to fall back on simply denying that many people would pay more.

BBC: Romney takes all in Las Vegas?

This creates a self-sustaining negative feed back loop as prices fall, produces cut back production, creating more unemployment, reducing demand, which increase deflationary pressures.

FORBES: American Political Economy Alters English Language