1. the quality or power of producing a desired or intended effect; effectiveness.
Usage: formal or technical; often used in medical, pharmaceutical, or scientific contexts

Examples

• The efficacity of the new vaccine was demonstrated in clinical trials.
• Doctors questioned the efficacity of the treatment for this particular disease.
• The efficacity of the drug depends on proper dosage and patient compliance.
• Research has confirmed the efficacity of regular exercise in reducing heart disease risk.
• The team evaluated the efficacity of different marketing strategies.