efficiency

American  

[ih-fish-uhn-see] / ɪˈfɪʃ ən si /

noun

plural

efficiencies

1. the state or quality of being efficient, or able to accomplish something with the least waste of time and effort; competency in performance.

2. accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort.

   The assembly line increased industry's efficiency.

3. the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage.

4. efficiency apartment.

---

efficiency British  

/ ɪˈfɪʃənsɪ /

noun

1. the quality or state of being efficient; competence; effectiveness

2. the ratio of the useful work done by a machine, engine, device, etc, to the energy supplied to it, often expressed as a percentage See also thermal efficiency

---

efficiency Scientific  

/ ĭ-fĭsh′ən-sē /

1. The ratio of the energy delivered (or work done) by a machine to the energy needed (or work required) in operating the machine. The efficiency of any machine is always less than one due to forces such as friction that use up energy unproductively.

2. See also mechanical advantage

3. The ratio of the effective or useful output to the total input in any system.

---

Other Word Forms

• nonefficiency noun
• superefficiency noun

Etymology

Origin of efficiency

First recorded in 1585–95; from Latin efficientia, from efficient- (stem of efficiēns efficient ) + -ia -y ³

Explanation

Efficiency is avoiding a waste of time, effort, or resources. Many people have begun to use compact fluorescent light bulbs because of their greater energy efficiency. Nowadays, efficiency often refers to energy efficiency, the effort to get more energy from existing resources: making cars that can go farther with less fuel, or appliances that do the same work with less electricity. But this noun isn't restricted to an environmental context. Efficiency can also simply be a measurement of what goes into a thing versus what comes out of it. A process with high efficiency requires only a little work to produce big results.

Example Sentences

However, earlier versions of piezoelectric converters have had difficulty maintaining efficiency and delivering sufficient power when handling large voltage differences.

From Science Daily • Apr. 10, 2026

“While AI will transform how we execute testing and improve efficiency, audit quality ultimately depends on human judgment, professional skepticism and accountability,” Bible said.

From The Wall Street Journal • Apr. 10, 2026

"With this comprehensive picture, we are finally able to reconcile many previously conflicting observations about lead-halide perovskites, resolving a long-standing debate about the source of their superior energy-harvesting efficiency," says Rak.

From Science Daily • Apr. 10, 2026

Under the party's proposals, individual councils would be given the power to cap excessive rents for their local market and renters would be given a new right to demand energy efficiency improvements.

From BBC • Apr. 9, 2026

I needed to know what kind of power efficiency the rover/trailer will get.

From "The Martian" by Andy Weir

Related Words

• ability
• adaptability
• capability
• competence
• energy
• expertise
• performance
• productivity
• readiness
• skill
• talent