Both conditional and provisional refers to situations where something is granted or provided before it is supposed to have fully and irreversibly granted or provided.
However, they are slightly different. If something is conditional, a precondition has to be met in order for something to happen.
If something is provisional, the same event happens but it is verified or nullified by a fact arising later.
Examples:
A conditional contract only becomes enforceable in the case of the prior performance of another agreement or clause.
The divorcing father was given provisional custody of his son pending a final order of dissolution is made.
