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concavo-concave,
concave,
concave lens,
concave polygon,
concave polyhedron,
concave shape,
concavo-convex,
converging concavo-convex,
diverging concavo-convex,
double concave,
concave figure,
made concave,
make concave,
makes concave,
making concave,
concave figures,
convexo-concave.