The origin of X in algebra. Why we say ‘how come’ for ‘why.’ Water handles.
Grammar Girl: For Writers and Language Lovers.
Mignon Fogarty, Inc.
4.5 • 2.9K Ratings
🗓️ 23 December 2025
⏱️ 18 minutes
🧾️ Download transcript
Summary
1144. This week, we look at the origin of the letter X as the variable for the unknown in algebra. Then, we look at the phrase "how come," explaining why it's more informal than "why" and how its grammar subtly differs from other question words.
That X segment was written by Peter Schumer, Professor of Mathematics and Natural Philosophy at Middlebury College, and it originally appeared on The Conversation and appears here through a Creative Commons license.
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Transcript
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| 0:00.0 | Grammar Girl here. I'm In Yon Fugherty, your friendly guide to the English language. Today, we're |
| 0:11.0 | going to look at why the letter X stands for the unknown in algebra, plus some X-related word |
| 0:17.0 | info, and then we'll look at why we say how come for why. But first, did you know that right now |
| 0:24.1 | you can get a free month of the Grammar Girl Patreon? And when you do, you also get a free super |
| 0:30.2 | list of 100 books that are the best books our podcast guests have ever read. When you're |
| 0:37.0 | finally relaxing and getting ready to settle in with a |
| 0:39.8 | good book before the new year, you'll love this list. The links are in the show notes, which is also |
| 0:45.6 | called the show description or the episode details on some platforms. This first segment is by |
| 0:51.9 | Professor of Mathematics, Peter Schumer. |
| 1:10.7 | Even though X is one of the least used letters in the English alphabet, it appears throughout American culture, from Stanley's X-Men superheroes to the X-Files TV series. The letter X often symbolizes |
| 1:12.9 | something unknown with an air of mystery that can be appealing. Just look at Elon Musk with |
| 1:18.9 | SpaceX, Tesla's Model X, and now X as a new name for Twitter. You might be most familiar |
| 1:25.7 | with X from math class. Many algebra problems use X as a variable to stand in for an unknown quantity, but why is X the letter chosen for this role? When and where did this convention begin? Well, there are a few different explanations that math enthusiasts have put forward, some citing |
| 1:46.0 | translation, others pointing to a more typographic origin. Each theory has some merit, |
| 1:52.8 | but historians of mathematics, like me, know that it's difficult to say for sure how X got |
| 1:58.8 | its role in modern algebra. Algebra today is a branch of math in which |
| 2:04.6 | abstract symbols are manipulated, using arithmetic to solve different kinds of equations. But many |
| 2:12.2 | ancient societies had well-developed mathematical systems and knowledge without symbolic notation. |
| 2:19.9 | All ancient algebra was rhetorical. |
| 2:24.0 | Mathematical problems and solutions were completely written out in words as part of a little story, |
| 2:30.7 | much like the word problems you might see in elementary school. |
| 2:36.9 | Ancient Egyptian mathematicians, |
... |
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