How did X come to mean “The UNKNOWN”?



A truly X-cellent and X-ceptional video…
Join our Patreon community:
↓↓↓ More info and sources below ↓↓↓

Despite being one of the rarest letters in English, the letter X is everywhere. We sign letters with it, we rate movies with it, we name all sorts of things after it. We’re kind of obsessed with it. And that’s probably all thanks to math, where X stands for the unknown. Let’s explore the bizarre history of how X took on this role…

References:

SUBSCRIBE so you don’t miss a video! ►►

———–

High fives to all our Brain Trust Patrons:

Charles Horton, Jr
Holly, Brett, and Ashe Bullion
Jaap Westera
Millennial Glacier
Mehdi Damou
Barbora Bei
Burt Humburg
dani bowman
David Johnston
Baerbel Winkler
Robert Young
Eric Meer
Karen Haskell

Join us on Patreon!

Twitter

Instagram

Merch

Facebook

source

37 Comments

  1. So now you know how X took over math, but let's give it some love in regular language: Post your favorite word containing X below! Mine is equinox

  2. X is to replace the pronunciation ch (ck) in Latin (and English language) shaya' ( شيء) which means "something" in Arabic language ..
    So X = something (unknown) (which needs to be found)

  3. 4:31 I don't think anyone here understands arabic… But as a native, man, he's even explaining why it's called “division” in a linguistic way 🫠

    Plus, I think this piece of paper is recent, cause an alternative letter we use nowadays in arabic is used instead of x, “ س ” (Seen). Maybe because in the past arabic was written without dots, so “ش ” (sheen) was written literally as same as “ س ” (seen).

  4. Thank you for sharing this!
    As a Persian, I was always wondering why Al-Khwarizmi, who was Persian, wrote in Arabic instead of Persian especially since we already had our own language and alphabet.
    But then I realized that at that time, Arabic was the language of knowledge and science.
    So he wrote in Arabic because he wanted his work and ideas to be shared, read, and understood by as many people as possible.

  5. Civil engineer, here.

    Algebraic variables, or letters as they are known, are chosen and used kind of arbitrarily.

    The fact that X was chosen as "unknown"…for arbitrary reasons.

    I.e. I wouldn't worry about this too much. Just get good at algebra — this is the golden prize !

  6. I always thought it was a bit of a pity that the letter that caught on to be the quintessential unknown letter already had several functions, even in terms of calculation – X is also a multiplication symbol (I remember having to use cursive versions of it to distinguish it as a variable, which isn't always easy if I'm entering an answer digitally) and the Romans also used it to represent the fixed value of 10 (I remember using it as the Roman numeral once and having someone try to "correct" me that it's actually an unknown value). Somewhat ironically, it seems attempting to choose an unusual letter to use as the default unknown value led to the choice of one which is actually strangely overworked.

  7. I used to like a show called Psi Chronicles. Total X files ripoff, but it was explaind that Greeks used psi like we use X. Fuckifiknow…

Leave a Reply

Your email address will not be published. Required fields are marked *

You might like

© 2026 Cantinho do Vídeo - WordPress Video Theme by WPEnjoy