Khafi — cause: an external factor obscures application; response: investigate.
Example: whether tarrar or nabbash falls under sariq.
Mushkal — cause: uncertainty within usage; response: investigate, then reflect.
Example: the scope of idam in an oath.
Mujmal — cause: intention cannot be fixed without the speaker; response: seek clarification.
Example: the legal specification of riba.
Mutashabih — cause: the strongest obscurity; response: withhold unwarranted certainty while assenting to the true intent.
Example: disconnected letters.
For every class, remember both the source of difficulty and the response appropriate to it.