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