transport number

symbol: $t$
https://doi.org/10.1351/goldbook.T06489
Of ions $\ce{B}$, the current density due to ions $\ce{B}$ divided by the sum of current densities of all the ions in the electrolyte. ISO recommends the name current fraction of ions $\ce{B}$.
Source:
Green Book, 2nd ed., p. 60 [Terms] [Book]