mathematical writing – Punctuation for describing symbols in math equations

I just can’t figure out what is the correct way to describe symbols in a math equation.

For example, I have an equation here

begin{equation}
text{SAR} =
frac{1}{V}
int_{text{sample}}
frac{sigma(mathbf{r})lvertmathbf{E}(mathbf{r})rvert}
{rho(mathbf{r})}dmathbf{r}
end{equation}

And now I want to define the symbols e.g. $sigma$, $rho$ etc. So usually, people write something like this below the equation:

“where $sigma$ is the sample electrical conductivity; $mathbf{E}$ is the gls{RMS} electric field; $rho$ is the sample density; and, $text{V}$ is the volume of the sample.”

Are you supposed to use semicolons to separate the clauses like above, or just commas? Do you add an ‘and’ before $text{V}$?