Causative

A team of investigators studies a sudden outbreak of food poisoning. They interview dozens of patients, test leftovers, and trace every ingredient. Finally, they discover that a specific batch of lettuce was contaminated with a rare bacteria. Without that lettuce, no one would have gotten sick. The lettuce is the direct, identifiable source of the illness. What kind of factor is the contaminated lettuce? It is a causative factor.

Causative refers to the direct source or specific mechanism that produces an effect. Active, by contrast, means currently in operation, exerting influence at this moment, regardless of being the original cause. Causative focuses on identifying the original agent or cause, while active focuses on present, ongoing force.