A relative form is definite, but its reference is normally completed by its relative clause. The clause may be verbal or nominal, and a returning pronoun (عائد) links it to the antecedent where needed. The relative word alone does not provide the full description intended by the speaker.
Examples:
«الذي اجتهد» — the one who exerted effort: a verbal clause.
«الذي أبوه عالم» — the one whose father is learned: a nominal clause.
«الذين نجحوا» — those who succeeded: a masculine plural relative.
The same grammatical device can identify, praise, disparage, or imply a reason. Its rhetorical force depends on how the clause relates to the context and the predicate.