Easy one this week, folks. It’s the difference between the action of backing up, building up, and the results thereof.
A few examples:
When you hold back on how you feel about small offenses, they’ll eventually build up — and lead to a blow up.
When you don’t make a backup of your files, you risk losing all your work.
Commercials that mention plaque buildup gross me out.
Sometimes you have to back up to move forward.
Notice the difference? When using “back up” or “build up” as a verb, it’s two words. As a noun — “backup” or “buildup” — you put them together for one word.
Think of it this way: Verb equals two words; noun, down to one.