- [obsolete] @A00472@ between a base and the conjugate acid of a different base through a @H02899@ (B' … HB+ or A'H … A−). The term has its origin in the @C01266@ and is in no way related to @C01267@ of @O04317@. Heteroassociation is a more appropriate term.
- [obsolete] Some authors refer to @C01267@ containing a heteroatom, e.g. pyridine, as 'heteroconjugated systems'. This usage is discouraged since it inappropriately suggests an analogy to @H02842@, and conflicts with the currently accepted definition of that term.