Englishfor English speakers
four
Determiner
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(ordinal fourth) The number 4. Four is one more than three and one less than five.
We have four fingers and one thumb on each hand.
four
Noun
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The number 4.
Two and two is four.
firm
Noun
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A firm is a group of people who work together as a business.
John &; John is a law firm.
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A firm is a group of people that come together to make money.
firm
Adjective
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A firm object is hard and solid.
concentration
Noun
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A concentration is a large amount of something in one place or group.
The oil-sands in Alberta, Canada, contain high concentrations of oil.
The growing concentration of people in cities is causing new problems.
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Concentration is the ability to focus your attention on something.
Runners mustn't worry or do anything else to break their concentration.
A clean desk in a quiet place will help students improve concentration.
The government's concentration should be on helping those in the greatest need.
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The amount of solute in a solution; the concentration of a solution is measured in parts per million (ppm)
ratio
Noun
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A ratio is the comparison in size or number between two things. It is written mathx:y/math and read mathx/math to mathy/math. It is the same as the fraction math\frac {x} {y}/math.
The ratio of men's jobs to women's is 8 to 1.
But Germany now has one of the highest ratios of spending to GDP in the European Community.
The low student/teacher ratio makes this a great school.