substituent

[suhb-stich-oo-uh nt] /sʌbˈstɪtʃ u ənt/
noun
1.
Chemistry. an atom or atomic group that takes the place of another atom or group present in the molecule of the original compound.
adjective
2.
having been or capable of being substituted.
Origin
1890-95; < Latin substituent- (stem of substituēns), present participle of substituere to substitute, equivalent to sub- sub- + -stitu-, combining form of statuere to set up, erect (see statue) + -ent- -ent
British Dictionary definitions for substituent

substituent

/sʌbˈstɪtjʊənt/
noun
1.
(chem) an atom or group that replaces another atom or group in a molecule or can be regarded as replacing an atom in a parent compound
adjective
2.
substituted or substitutable
Word Origin
C19: from Latin substituere to substitute