On what ground can you say that scandium $(Z=21)$ is a transition element but zinc $(Z=30)$ is not?

(N/A) transition element is defined as an element which has incompletely filled $d$ orbitals in its ground state or in any one of its oxidation states.
Scandium $(Z=21)$ has the electronic configuration $[Ar] 3d^1 4s^2$. Since it has an incompletely filled $3d$ orbital,it is considered a transition element.
Zinc $(Z=30)$ has the electronic configuration $[Ar] 3d^{10} 4s^2$. In its ground state and its common oxidation state $(Zn^{2+}: [Ar] 3d^{10})$,the $d$ orbitals are completely filled. Therefore,it is not considered a transition element.