The term was originally applied to describe the maximum flocking of either hard or soft ligands in the same complexes. For hydrocarbon molecules, symbiosis implies that those containing a maximum number of C–H bonds (e.g. CH4) or C–C bonds (e.g. Me4C) are the most stable.
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1170 (