# side chain

> English word · Noun

## Definitions
1. That part of a molecule attached to some core structure; a radical.
2. Any of the variable parts of amino acids that extend from the peptide backbone in proteins; they are referred to as R-groups, which branch off the backbone at the alpha carbon (Cα).
3. Auxiliary audio input fed to a synthesizer etc. and used to selectively trigger an effect.
4. A separate blockchain attached to a parent blockchain (mainchain) to extend its functionalities.
5. On some railways, a chain fitted on both sides of a centre coupler or buffer at each end of a rail vehicle, which has a hook for connection to a corresponding chain on the next vehicle in a train.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/side-chain