noun
a noun is a person, place, thing, or idea. In this case, 'concavity' is a noun referring to the quality of being concave or having a surface that curves inward.
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The concavity of the parabola can be determined by looking at the sign of the coefficient of the x^2 term.
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The concavity of this graph makes it look like a smiley face.
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The concavity of the road ahead is no joke, so drive carefully.
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Her concavity towards authority figures was evident in the way she always followed the rules.