咩係ionization???咩係dissocIation???

Ionization: formation of ions by separating atoms, molecules, or radicals, or by adding or substracting electrons from atoms by weakening the electric attraction in liquid, especially water or by strong electric fields in gas

e.g. HCl + H2O ---> H3O+ and Cl-

Dissociation: reversible or temporary breaking down of a molecule into simpler molecules, atoms, free radicals or ions.

e.g. 2NH3 <=> N2 and 3H2

Definition from dict.
Examples by myself.