Englishfor English speakers
sludge
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noun
the precipitate produced by sewage treatment
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noun
any thick, viscous matter
mass
Noun
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A measure of how much material is in something.
The Earth has much more mass than the moon.
The spacesuit weighed 75 pounds on Earth but here in outer space it weighed nothing, although its mass was exactly the same.
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Much material.
A mass of dirty branches stopped the river.
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A Christian ceremony in memory of .
He goes to mass every Sunday.
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A crowd of people.
A mass of protesters gathered at city hall.
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)