The refractive index of diamond is $2.42$. What is the meaning of this statement?

(N/A) The refractive index of a medium $n_m$ is related to the speed of light in that medium $v$ by the relation:
$n_m = \frac{\text{Speed of light in air}}{\text{Speed of light in the medium}} = \frac{c}{v}$
Where,$c$ is the speed of light in vacuum or air.
The refractive index of diamond is $2.42$. This suggests that the speed of light in diamond is reduced by a factor of $2.42$ compared to its speed in air.