Acyclic or cyclic, saturated or unsaturated carbon compounds, excluding aromatic compounds.
Aliphatic compounds can be saturated, joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). Besides hydrogen, other elements can be bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine.
The most important aliphatic compounds are:
n-, iso- and cyclo-alkanes (saturated hydrocarbons)
n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons).