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efficient

/ɪˈfɪʃnt/·adjective

achieving the result with minimal waste of energy, time, or effort
Fig. 1 — Two lamps on one shelf give exactly the same light — the meter under each reads 800 lumens, and neither cone of glow is larger.
01Definition

Efficient describes what does its job with the least possible waste — of fuel, time, money, or motion. It is a ratio word: output against input. An efficient engine turns more of its fuel into movement; an efficient worker produces the same report in half the afternoon; efficient systems minimize waste while output stays whole. From Latin efficere, 'to accomplish'. Its neighbour effective asks a different question: whether the thing works at all. A plan can be effective but wasteful, or efficient and pointless — the compliment worth earning is both.

02In use
  • iLED bulbs are efficient enough to repay their price within a year.
  • iiHer efficient reading — twenty minutes, three highlighted passages — beat his afternoon of pages.
  • iiiThe new border checks were thorough but so inefficient that trade simply rerouted.
03Collocations
  • energy-efficient
  • fuel-efficient
  • an efficient use of
  • highly efficient
  • cost-efficient

Family efficiency (noun) · efficiently (adverb) · inefficient (adjective)

04Relations

=economical, streamlined, productive, resourceful, lean

≠wasteful, inefficient

06TOEFL & IELTS

Energy essays run on the compounds: energy-efficient appliances, fuel-efficient cars, and the noun phrases energy efficiency and 'a more efficient use of resources' — Task 2 staples that outrank plain 'good'. Prepositions: efficient IN + noun ('efficient in its use of water'), efficient AT + gerund ('efficient at converting sunlight'). Second-syllable stress, ih-FISH-ent, with -cient as one /ʃənt/ sound. Keep the effective distinction ready: effective = it works; efficient = it works without waste.

07Asked
What is the difference between efficient and effective?
Effective means it achieves the intended result; efficient means it achieves it with minimal waste. Peter Drucker put it best in a 1965 lecture: effectiveness is doing the right things, efficiency is doing things right. Both lamps in the scene above are effective — 800 lumens each — but only the 9-watt one is efficient. A treatment that cures at enormous cost is effective, not efficient; a beautifully lean process that fixes the wrong problem is the reverse.
What does efficient actually measure?
A ratio: useful output against total input. Nothing is efficient in the abstract — it is efficient at converting fuel to motion, time to output, budget to results. That is why engineers can put a number on it (a petrol engine converts roughly a quarter to a third of its fuel's energy; the rest leaves as heat) and why the word carries an implicit comparison: more of what you paid for, less lost along the way.
Can a person be efficient, or only machines and systems?
People wear it naturally: an efficient administrator wastes neither your time nor hers, and the compliment is about method, not talent. That separates it from proficient, which praises skill — a proficient translator knows the languages deeply; an efficient one delivers on Thursday. One can be proficient and slow, or efficient and shallow; job adverts asking for both know the difference.
What does energy efficiency mean?
Getting the same service from less energy — the same warm house, the same 800 lumens, the same washed clothes, on fewer watts. It is measured as a ratio (useful energy out over energy in) and sold as ratings on appliances. The International Energy Agency calls efficiency 'the first fuel', and the industry slogan runs that the cheapest kilowatt-hour is the one you never use; insulation, LEDs, and heat pumps are efficiency's flagship examples.
What is the noun — efficiency or effectiveness?
Each adjective keeps its own: efficient gives efficiency (minimal waste), effective gives effectiveness (achieving the goal), and careful writing never swaps them — a treatment is judged on effectiveness, an engine test on efficiency. Medicine adds a third: efficacy, performance under the ideal conditions of a controlled trial, as against effectiveness in the messy real world. The adverb is efficiently; the negative, inefficient, is often the sharper essay tool.
What does 'market efficiency' mean in economics?
A specialized cousin of the everyday sense: a market is called efficient when prices already reflect available information, so no waste — and no easy profit — is left lying around. Allocative efficiency — economists also call it Pareto efficiency — is closer to the ordinary meaning: an allocation is efficient when nobody can be made better off without making somebody else worse off. Both keep the core idea: nothing usable going spare.