Here are the definitions I use.
Ionization is the conversion of a neutral molecule or atom to an ion.
Thus, the conversion of an
This is also a dissociation process.
Dissociation is a process in which a compound separates into two or more parts.
For example, water dissociates into hydronium and hydroxide ions.
Here's a great video that shows how water dissolves salt.
Dissolution is the process in which the particles of a substance move into the solvent.
The process may not involve dissociation, as in the dissolving of sugar …
… or it may, as in the case of sodium chloride.
Sugar does not dissociate in water, but