substituent

[sสŒbหˆstษชtสƒuษ™nt]

IPA: /S AH1 B S T IH1 CH UW0 AH0 N T/

noun
  1. 1

    Any atom, group, or radical substituted for another, or entering a molecule in place of some other part which is removed

  2. 2

    (grammar) pro-form

Source: https://en.wiktionary.org/wiki/substituent