Technology / Aviation / Tetrahedron: Ground-based, free-rotating, triangular-shaped wind direction indicator, generally placed near a runway, often lighted at major airports.
Science / Geology / Clay: A clastic mineral particle of any composition that has a grain size smaller than 1/256 mm. The term is also used in reference to a broad category of hydrous silicate minerals in which the silica tetra MORE
Science / Chemistry / Tetrahedral: A molecular shape that results when there are four bonds and no lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the corners of a tetrahedron with 109.5Â MORE