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ne 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. -- Hem`i*he"dral*ly, adv.

Presenting hemihedral forms, in which all the sectants have halt the whole number of planes. Dana.

A solid bounded by twelve quadrilateral faces. It is a hemihedral form of the isometric system, allied to the tetrahedron.

A solid bounded by twenty-four similar quadrilateral faces. It is a hemihedral form of the hexoctahedron.

i. e., related to each other as a right-handed to a left-handed glove; -- said of certain hemihedral crystals.

y, so that they incline all to the right (or left) of a vertical line; -- said of certain hemihedral forms.

The property of crystallizing hemihedrally.

A solid hemihedrally derived. The tetrahedron is a hemihedron.

Presenting hemihedral forms, in which half the sectants have the full number of planes.

Having all the planes required by complete symmetry, -- in opposition to hemihedral.

Like pyrites in hemihedral form.

A wedge-shaped crystal bounded by four equal isosceles triangles. It is the hemihedral form of a square pyramid.

Pertaining or related to a tetrahedron, or to the system of hemihedral forms to which the tetrahedron belongs. Tetrahedral angle (Geom.), a solid angle bounded or inclosed by four plane angles.