Efficacy: meaning, definitions and examples

Use 'efficacy' when describing the ability of something to produce a desired or intended result, especially in the context of medicine, treatments, or interventions.

• The efficacy of this new vaccine has been proven in clinical trials.
• Researchers are studying the efficacy of the drug in treating rare diseases.

Use 'effectiveness' to describe how well something achieves its intended goal, often in a broader, practical context, such as policies, teaching methods, or programs.

• The effectiveness of the new policy will be evaluated at the end of the year.
• We need to assess the effectiveness of our marketing strategy.

Use 'potency' to discuss the strength or power of something, particularly in relation to drugs, chemicals, or other substances, and sometimes it can have a negative connotation related to danger or toxicity.

• The potency of the painkiller means that it should only be used under strict medical supervision.
• They measured the potency of the new fertilizer in boosting crop yields.

Use 'efficiency' to talk about the ability to achieve a goal with minimal waste of time, resources, or effort, often in business, engineering, or economics.

• The new process has improved the efficiency of production significantly.
• Energy efficiency is a key consideration in modern housing design.

Used to describe the ability to produce a desired or intended result, often in formal or technical contexts such as medicine or research.

• The efficacy of the new drug has been proven in several clinical trials
• Researchers are still evaluating the efficacy of the new vaccine

Describes how well something achieves its intended purpose or results, often in practical or everyday situations.

• The effectiveness of this marketing strategy is evident from the higher sales figures
• We're evaluating the effectiveness of the new training program

Implies strength, control, or influence over others or situations; can also refer to physical strength or potency.

• He has the power to make important decisions in the company
• The power of the storm caused widespread damage

Used to describe the power or ability to do something, often in terms of skills, tools, or resources available.

• The software has the capability to handle multiple users at once
• She has demonstrated her capability in managing the project efficiently