JS Tip 252: From the Writing Workshops: Semi-weekly and Bi-weekly

We appreciate your suggestions and questions.

Ted Kohlmann of BioFire asked, “Could you explore semi-weekly and bi-weekly? Which one means ‘once every two weeks’ and which one means ‘twice a week’? 

“The same questions apply to ‘semi-monthly,’ ‘bi-monthly’ ‘semi-annually,’ and ‘bi-annually,’”

We can do this.  

Semi- means “half,”* so semi-weekly means “twice a week” (or “once every half a week” but that sounds goofy).

Bi- means “two,” so bi-weekly means “every two weeks.”

But no one understands this. The terms have been misused so often that no one fully understands what they mean. Everyone gets confused.

So we suggest (and The Chicago Manual of Style suggests) that you avoid the confusion: Don’t use the words.

Instead of semi-weekly, write “twice a week.”

Instead of bi-weekly, write “once every two weeks.”

There’s no confusion with those. As for the others—

Instead of semi-monthly, write “twice a month.”

Instead of bi-monthly, write “once every two months.”

Instead of semi-annually, write “twice a year.”

Instead of bi-annually, write “once every two years.”

Bi-annually has an interesting cousin: biennially. It’s an attempt to clear up the confusion, and it still means “once every two years.” But can you be sure your reader will understand that? Use “once every two years.”

We don’t usually want to add words to a document, but, in this case, we’ll reluctantly sacrifice brevity for clarity.

We love this stuff. We appreciate you.

Next week, we’ll tackle to, two, and too, and you’re and your. Maybe yore.  

* A semi-trailer has wheels on half—the rear half—of the trailer.