JS Tip 489: Semi-weekly and Bi-weekly

From the Writing Workshops: Semi-weekly and Bi-weekly

Something simple. 

It’s been a while since we've talked about this. Years, in fact.  

Think fast: 

How often is semi-weekly? 

How often is bi-weekly? 

Which one means “once every two weeks” and which one means “twice a week”?  

Most people answer honestly: “I have no idea.” 

Okay. Here we go. 

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 the terms have been misused so often that no one 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.” 

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

Next week, we’ll talk about biannual, semiannual, and biennial. 

We love this stuff. We appreciate you.

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