It may be 2019, but humans are still trying to figure out the best ways to write emails. Do you start off by saying "Dear So-and-So" or just a simple, "Hey!"? Do you put "Sincerely" at the bottom? How long an email is too long? If you're someone who thinks about these things a lot, then we have to share with you one two-letter word you should never use in your professional emails.
According to one "internet linguist," which is apparently a thing, the two-letter word you should never use in your professional emails is "Ok." Gretchen McCulloch says "Ok" can come off as passive-aggressive or flippant. The word itself isn't bad, as much as the brevity of it. It's better to say, "Ok, sounds good," or something like that instead. You can even put an exclamation mark after the "Ok" to make it come off as less aggressive.
"Anything that's shorter can sound curter. Anything that's longer can sound more polite," McCulloch says.
Interestingly enough, McCulloch even says saying, "kk" is better than just "Ok," because it sounds more casual and friendly.
But there are exceptions to this this rule. If you notice your boss or manager replies to emails using only, "Ok," then you should be alright to do so as well. This is called "mirroring" where you copy a person's style in emails to make it more socially acceptable.
And here we thought the two letters you should never use were going to be, "F U."
(h/t Mental Floss)