Lognormal distribution

A random variable whose logarithm is normally distributed

$\mu$
$\sigma$
$$ f(x)=\frac{1}{x\sigma\sqrt{2\pi}}\exp \bigg(-\frac{(\ln x-\mu)^2}{2\sigma^2}\bigg) \\[16pt] \text{where $\mu$ is the mean and $\sigma$ is the standard deviation of a} \\ \text{normally distributed random variable $Y$ such that $Y=\ln X$.} $$