The quality or condition of being biconcave; the state of being inward-curved on both sides.
From 'biconcave' plus the suffix '-ity,' which transforms an adjective into a noun expressing a state or quality. This technical term is used in optics and anatomy.
The biconcavity of certain lens designs allows them to diverge light rays at precise angles—eyeglass makers carefully calculate this property to correct nearsightedness, making glasses that actually work.
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