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Hemihedral

Definition: Having half of the similar parts of a crystals, instead
of all; consisting of half the planes which full symmetry would
require, as when a cube has planes only on half of its eight solid
angles, or one plane out of a pair on each of its edges; or as in the
case of a tetrahedron, which is hemihedral to an octahedron, it being
contained under four of the planes of an octahedron.