Englishfor English speakers
cell
Noun
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A cell is a room in a jail where prisoners are kept.
He was arrested and kept in a small cell for one day.
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A cell is a unit of a living organism.
A plant cell has a cell wall.
radius
Noun
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A radius is a straight line between the centre of a circle and its circumference.
To find the area of a circle, you have to know the length of the radius.