Englishfor English speakers
efficient
Adjective
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If something is efficient, it can do a lot but uses very little time, energy, money, etc.
He wastes a lot of time talking, and isn't very efficient at work.
Smaller cars are generally more fuel-efficient than big cars.
cost
Noun
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The cost of something is the price that a person pays for it.
What is the cost of the car?
cost
Verb
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When you say that a thing costs, you say that one must pay in order to buy it.
That diamond ring costs a great deal of money.
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One may say that an action costs a certain bad result.
It cost me my job when I broke the machine.
To commit a crime will cost you.
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When you estimate a cost or set a cost, you cost a thing.
The repair man costed the work to fix the car.