Saturday, 3 November 2012

Why is 'x' the Unknown?

It started in Maths class. "2+5=x. Find x." That's a statement we've all seen far too often. But it's not just algebra where x is unknown. It's everywhere else too. We have the X Factor, The X-Files, Project X, and so many more.

The question I'm sure a lot of people have asked is "Why does the letter 'x' represent the unknown?"

Algebra was around thousands of years ago, but it didn't make its way into western society, and more specifically, Europe, until the 1100s. Algebra came from the Arabs, from the word الجبر (al-jabr).

In the Arabian algebra, they used a word to describe the unknown variable. الشيء which means "the unknown thing".

The system of Algebra made its way to Spain in the 1100s, where mathematicians wanted to translate it into a European language. They tried to translate algebra into Spanish, where they came across a complication. You see, the first letter of the word for the unknown thing makes a sh sound. The word for the unknown thing has a sh sound in it.

That sound does not exist in Spanish. So the Spanish scholars had to make a compromise. Instead they used a ck sound. They borrowed the Greek letter Chi, which just so happens to look like an x. And that represented the unknown thing.

So when they translated algebra into a more common language (Latin); they simply replaced the Greek Chi with the Latin x.

Once algebra was in Latin, it was printed in textbooks that way for hundreds of years.

So the answer is:

X is the unknown because you can't say sh in Spanish.

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