I’m working on an article about setting up good backup procedures for your writing files. Of course, as soon as you start writing about backup (which is different from back up), the careful writer can get into trouble—although the problem might only be one of confusing yourself or others by alternating the one-word and two-word spellings. I’ve seen plenty of writers, even—perhaps particularly—on technology websites, get this wrong.
However, there is a difference between the two, and there’s an easy way to tell them apart. As one word, backup, it serves as a noun or adjective:
- My backup of my files is stored in a secure location. (noun)
- I have backup copies of my writing in multiple locations. (adjective)
However, if you want to use this term as a verb, you need to use the two-word form, back up:
- Careful writers back up their files frequently. (verb)
The reason the verb form needs to be two words should be obvious when you consider that verbs need to go through all those various tenses—you know, all that conjugation stuff that you hated in school. So:
- I back up my files.
- He/she backs up his/her files.
- We back up our files.
- They back up their files.
That’s not so bad, as only the third person singular (he/she) in present tense has a changed (inflected) ending, but what about these:
- I’m backing up my files.
- She backed up her files to the cloud yesterday.
- He backs up his files daily.
- You should be backing up your files regularly.
Common sense shows us that the inflected ending goes onto back and not up, and thus the need for keeping these as separate words. Imagine the chaos—and hilarity—if we treated the one-word backup as a verb:
- I backupped my files.
- She backups her files to the cloud and a thumb drive.
- Last time I saw him, he was hiccupping while backupping his files.
Or imagine the pain on the eyes and brain it might cause trying to parse the meaning of a verb with the inflection grafted into the middle:
- He forgot he had backedup his files already.
- I’m tired of backingup my files, but I do it anyway.
If it sounds silly, it probably is. But now you should see that there is a logical way of determining which version you need in a particular instance: Try a verb ending on back in the sentence construction you have. If it works, you’ve got the two-word verb; if not, you’ve got a noun or adjective form, so keep it as one word. I hope this helps.
I don’t know and won’t delve into the reason that the noun/adjective form gets to be a single word, although I think there is a tendency to combine compound forms into single words over time, and this could be one such case. English is such a fun language, right?
Follow B. K. Winstead on Twitter at @bkwins