Bessel function's roots

Question

The Bessel functions are denoted as $J_n(x)$ where $n$ is the nonnegative value of order, and $j_{nm}$ are the roots of the function. I don't get the notation $m$ in here. What does the $m$ index represent?

Answer 1

The $J_n(x)$ has an infinite number of roots similar to $\sin(x)$ and $\cos(x)$ and they are numbered in order so $j_{n1}$ is the first positive root of $J_n(x)$ and so on.