Why is it X?

Question

Why is x the letter everyone uses? It is the main variable, it is an axis, why x? Anyone with little tidbits of knowledge know the answer?

Answer 1

I concur with the above answer, that it may be because x stands out.

But other letters are used too, lowercase, uppercase, and Greek letters. In fact, I think the only letters that have negligible if any use are lowercase L (since it can be mistaken for the digit one) and O, since it looks like zero.

And some letters are reserved for constants, such as e, i, and the Greek lowercase letter pi.

In fact, different letters are generally used for specific purposes. j, k, m, and n typically represent integers, while a, b, c, and d can be used to represent real-valued parameters (like if you want to express a family of functions), f, g, and h are typically functions.

Answer 2

I think when Descartes wrote his original treastise on analytic geometry, he used x and y for the labels on his axes, and the tradition stuck.

Eventually the custom arose to use letters at the end of the alphabet for variables and letters at the beginning of the alphabet for constants. Thus, when we see the problem

solve ax^2 + bx +c =0

our instinct is to solve for x, not to solve for b!

Answer 3

it can really be any letter that u want it to be, but i guess all the smart math people just leave it as X

Answer 4

maybe because x is a rare letter to use in a sentence / story ..... and x stands out

Answer 5

X is a special letter, ( mm or so they say)

Answer 6

dunno. x marks the spot?