\begin{definition}[Definition:Bessel Function/First Kind]
A '''Bessel function of the first kind of order $n$''' is a Bessel function which is non-singular at the origin.
It is usually denoted $\map {J_n} x$, where $x$ is the dependent variable of the instance of '''Bessel's equation''' to which $\map {J_n} x$ forms a solution.
\end{definition}