Crafting business emails or other professional correspondence can be a tricky balancing act. Should you close an email with "best" or "kind regards"? Are emojis ever acceptable? Is "per my last email" a fair way of calling attention to an overlooked point, or is it a thinly veiled jab at the recipient?

We've previously written about the dangers of using all caps in emails (in summary: don't do it), but there's something else you should be wary of while cranking out a quick note to your boss or colleague. As internet linguist and author Gretchen McCulloch tells the Huffington Post, using "OK" in an email isn't, in fact, OK.

That's because short replies can come off as flippant or passive-aggressive, she explains. The word itself isn't necessarily rude, but the brevity can be problematic. It's far safer to tack another word onto your reply, like "OK, great" or "OK, sounds good." You can throw in an exclamation point to show enthusiasm, but by all means, avoid the dreaded "k."

As a general rule, McCulloch states, "Anything that's shorter can sound curter. Anything that's longer can sound more polite." Oddly enough, even "kk" is preferable to "OK" in McCulloch's eyes because it softens the delivery, in much the same way that "bye-bye" sounds nicer than "bye." This word repetition even has a name for it in linguistics: reduplication.

Of course, there are exceptions, and your correspondence may vary depending on who you are emailing. If your boss or client uses "OK," then it's probably fine for you to use it, too. This technique, called mirroring, is usually a safe bet. "Generally what I try to do in emails is mirror what the other person is doing," McCulloch says. "If I see someone else saying things like "ok cool," I can do something in that family."

If you're looking for a few more pointers to give your emails a boost, check out this guide to email etiquette, as well as the phrases you should never use if you want to get a response.

[h/t Travel + Leisure]