# AIC and categorical predictors

As we know, the AIC is defined as $\mathrm{AIC} = 2k - 2\ln(L)$ with $k$ being the amount of estimated parameters.

My question is: in case I have a categorical predictor, lets say: educational backgroud, with three categories. Does this count as 1 or as 3 estimated parameters in the AIC's sense?

That is, suppose educational background takes values low, medium, high, then you might end up with two binary dummy variables: isLow, isMedium. Thus, the number of parameters k is 2.