|Label||Type (orthogonal)||Label||Type (non-orthogonal)|
| || ||AO||Atomic Orbital ("the" basis set of host electronic structure system).|
|NAO||Natural Atomic Orbital||PNAO||Pre-orthogonal* NAO|
|NHO||Natural Hybrid Orbital||PNHO||Pre-orthogonal NHO|
|NBO||Natural Bond Orbital||PNBO||Pre-orthogonal NBO|
|NLMO||Natural Localized Molecular Orbital||PNLMO||Pre-orthogonal NLMO|
|MO||Molecular Orbital (canonical; delocalized)|| || |
*The pre-orthogonal orbitals (lacking only the final interatomic orthogonalization step of the NAO algorithm) resemble the idealized "textbook" shapes and their overlaps suggest the qualitative strength of orbital interactions.