Defined for ionic species B by $\lambda =|z_{\text{B}}|F{u}_{\text{B}}$ where $z_{\text{B}}$ is the charge number of the ionic species B, $F$ is the Faraday constant, and $u_{\text{B}}$ is the electric mobility of species B. In most current practice $z_{\text{B}}$ is taken as unity, i.e. ionic conductivity is taken as that of species such as Na⁺, Ca²⁺/2, La³⁺/3 etc. To avoid ambiguity the species considered should be clearly stated, e.g. as $\lambda ({\text{Ca}}^{\text{2+}}/2)$.