# 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 $$text{V}$$?