On Monday, Twitter user Abdul Dremali tweeted an observation about the division symbol that quickly went viral for making everyone see their childhood math lessons differently.
According to BuzzFeed, there's some anecdotal truth to this idea. While the symbol, known as an obelus, was once used to signify uncertainty in a quotation or even subtraction, it isn't clear why it was eventually adopted as a division symbol in 1659. But math teachers have used it ever since to help teach students that division is just making two numbers into a simplified fraction—and it isn't the only symbol in which Twitter users have noted a clever design.
And guess what—‰ is called the permille and ‱ is called the permyriad. You can see how they get their names—per cent means per hundred and per mille means per thousand, derived from Latin. A "myriad" is an outdated way to say ten thousand.
That one's not technically math, but I bet you never realized that (or, at least I didn't). For many of these, I just wish I knew the meanings of the symbols when I was struggling in elementary school math.