Via a quick check in the thesaurus, it returned the terms 'specific' and 'specificity'. What I have in mind is 'specificalization', but that word does not exist.
In logic, the opposite to generalization is instantiation. When you have shown than something is true of an arbitrarily chosen individual, the rule of universal generalization allows you to infer that it is true of all individuals. When you know that something is true of all individuals, universal instantiation allows you to infer that it is true of any arbitrarily chosen individual.