A circumstance associated with a rule may exist, yet a required condition for applying it to a particular person may be absent. Even where a relevant cause and condition are present, an impediment can block a legal consequence.
Useful distinctions:
Sabab: a prescribed occasion or connecting factor for the rule.
Shart: a condition required for the relevant legal status or validity.
Mani: an obstacle preventing the consequence despite the apparent occasion.
Confusing them can produce serious errors in applying a ruling.