What's the difference between "OK" "Ok" "OK!" "K" and "kk"? They all communicate the same thing--yes, all right--but some of them may cause unintended offense to Millennial and Gen-Zers in the workplace. Unfortunately, many in the older generations have no idea they're being hurtful.

I must be an old fuddy-duddy, but I had not noticed the difference between "OK," which I've been using my entire life, and the younger generations' "kk." Then one of my Millennial colleagues used "kk" twice in a row in a Slack conversation about scheduling. I had never thought much about "kk" and I certainly didn't know there was any good reason to choose it over more traditional expressions of agreement until I read a New York Times piece from the column "Work Friend," in which readers write in with work-related dilemmas, and a Millennial writer answers them.

In this week's column, a Gen-X correspondent asked about the following:

"I have been informed by my Millennial and Gen Z co-workers that the new thing I'm supposed to type is 'kk.' To write 'OK' or 'K,' they tell me, is to be passive-aggressive or imply that I would like the recipient to drop dead."

To my surprise, the column's author Caity Weaver confirmed that this is true, at least from a Millennial or Gen-Z point of view. Receiving the answer "OK" to a request by email, text, or chat feels rude to her. So does the common shortened version "K" which seems to indicate that the writer is too stressed out and pressed for time to be polite. But, she says, "You reply to an email with 'kk': I think 'OK.'"

In case you're wondering where "kk" came from, there are conflicting theories, but most seem to say that it's a shortened version of the popular 90s gamer expression "k, kewl," which is itself a shortened version of "ok, kewl." Wherever it came from, it does seem to be the most polite form of acknowledgement for the under-40 set. According to Urban Dictionary:

"Importantly, using 'kk' instead of 'Okay' avoids any suggestion of sarcasm or doubt. There are lots of ways of inflecting Okay. kk is just pure acknowledgement; your message is received. And it is fast to type."

Sarcasm or doubt?? OK, I have to admit I'm way up there at the young end of the Baby Boom generation, but I had absolutely no idea that any form of the word OK could be construed as sarcastic or doubtful. For decades, I lived right across the Hudson River from Kinderhook, New York; When I think about the term "OK" at all, I think about the failed re-election campaign of Martin Van Buren.

Clearly, I'm behind the times. I also didn't realize that different permutations of "OK" carry subtly different meanings. A Buzzfeed article by Alex Alvarez, undoubtedly a young person, spells them out:

"'Ok' is a classic. 'OK' is aggressive, but acceptable. 'Okay' is a waste of everyone's time. 'Ok!' is a necessary evil or a genuine display of enthusiasm, depending on the recipient."

And what about "K," a quicker version of "OK" sometimes used by my generation? Whatever you do, don't do that. Alvarez writes:

"'K' is so mean. So closed off. Judgmental. 'K' doesn't want to hear about your crush, or make the changes you suggested in your email. 'K' doesn't love you back. 'K' barely even cares."

Yikes!

So "kk" would seem to be the term of choice, but not "KK," which seems like shouting. Except there are also a lot of people who say they hate "kk." Weaver says she solves the problem this way:

"I myself kk rarely. I prefer 'OK!,' which feels more natural, but still conveys to the recipient, through its superfluous exclamation point, the same frantic message that I'm not annoyed or angry (omg why would I be) so please don't feel bad!!"