SP3 HYBRIDIZATION OF CARBON

In sp³ hybridization, one 2s and three 2p orbitals of excited carbon intermix together and form 4 hybrid orbitals which are oriented in tetrahedral geometry in space around the carbon atom. Each sp³ hybrid orbital is occupied by one electron.

Each of these sp³ orbitals can form σ-bond with other atom. Thus carbon is forming four single bonds with other atoms in tetrahedral geometry. The bond angles are usually equal to or nearer to 109^o28'.
E.g. In methane molecule, CH₄, the carbon atom undergoes sp³ hybridization and forms four σ-bonds with hydrogen atoms.

Note that whenever carbon atom undergoes sp³ hybridization, it forms 4 σ-bonds i.e., 4 single bonds.