Efficacy refers to the performance of an intervention under ideal and controlled conditions. It assesses whether an intervention produces the expected result under optimal circumstances.

Effectiveness measures the degree of beneficial effect of an intervention in real-world clinical settings. It evaluates whether an intervention works in terms that matter to the patient and is applicable to routine clinical practice.

Efficiency refers to the ability of an intervention to achieve desired outcomes with minimal resources, such as time, cost, or effort. It assesses the cost-effectiveness and resource utilization of an intervention.