What is the meaning of x in x ray?

Answer 1

The "x" is not an abbreviation of another word. It's the "x" from algebra,

which refers to any unknown quantity. Wilhelm Roentgen did not know

what had passed through his hand and accidentally produced an image

of the bones in his hand on a nearby piece of film, and he referred to

whatever it was as "X strahlen" ... German for "X rays" where 'X' means

'unknown'. In Europe X-rays are known as Roentgen rays.

X-Radiation is a form of electromagnetic radiation having a wavelength of

0.01 to 10 nanometers.

Answer 2

It meant unknown rays. Some persons who discovered this rays did not know what they were. This was long after Nikola Tesla was familiar with this ray. He took a picture of his hand before no one and even then, he didn't have a name for the ray.

Answer 3

"x" stands for the unknown in mathematics, which is why named them as such.