Answer
$s$ is called the spin quantum number.
$S$ is the spin angular momentum.
$S = \sqrt{s~(s+1)}~\hbar$
Work Step by Step
$s$ is called the spin quantum number of a particle.
For example, for an electron, $s = \frac{1}{2}$
$S$ is the spin angular momentum.
$S$ is related to $s$ as follows:
$S = \sqrt{s~(s+1)}~\hbar$
