sphenoid

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sphenoid A wedge-shaped, four-faced, closed form, normally occurring in the tetragonal or orthorhombic crystal systems, but with a special form (the ‘mono-clinic sphenoid’, or ‘dihedron’) occurring in the monoclinic system. The terminology for sphenoidal forms is complex and inconsistent, although in general the crystallographic axes emerge at the centre of the edges where pairs of triangular faces meet.

sphenoid

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sphenoid (anat.) irregularly-shaped bone at the base of the skull wedged in between other bones. XVIII. — Gr. sphēnoeidēs, f. sphēn wedge; see -OID
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