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》

If it waits another fraction of a second, the force of gravity will overtake inertia, causing the column to break, the liquid to fall back into the bowl, and the cat's tongue to come up empty.

如果它再等上几分之一秒，重力的作用将压倒惯性而破坏液柱，液体会落回碗里，而小猫的舌头则扑了个空。

youdao

The summer break would be from May to August. There is also Winter break for about three weeks (I will be back in Shanghai), a spring break and a fall break, both are one week long.

暑假则是五月到八月，还有大约两周多的寒假，各一周的春假及秋假。

youdao

But Spanish ace Nadal kept battling and got a lucky break in the fourth game of the decider as his U.S opponent's return hit the net cord and bounced back on his side of the net to fall down a break.

CNN: Tennis: Nadal survives scare as Djokovic goes out