$$\require{cancel}$$
In place of the semi major axis, we have the semi transverse axis, symbol $$a$$. This amounts to just a name change, although some authors treat $$a$$ for a hyperbola as a negative number, because some of the formulas, for example for the speed in an orbit, $$V^2 = GM \left( \frac{2}{r} - \frac{1}{a} \right)$$, are then identical for an ellipse and for a hyperbola.