Illustrated Glossary of Organic Chemistry

sp³ orbital: One of a set of hybrid orbitals produced when one s orbital and three p orbitals are combined mathematically to form four new equivalent orbitals oriented toward the corners of a regular tetrahedron.

The C-H bonds of methane are formed by overlapping a carbon sp³ orbital with a hydrogen 1s orbital. The resulting C-H bonds point to the corners of a tetrahedron, and have H-C-H bond angles of 109.5^o.