Side-chain, side chain, or sidechain may refer to: Side chain, a chemical group attached to the main chain or backbone of a molecule, such as a protein Substituent, an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon Side-chaining, an effect in digital audio processing Sidechain (ledger), a designation for a particular blockchain See also Backbone chain Branching (polymer chemistry) Pendant group