Editing Bracket (section)

====Chemistry====
Parentheses are used in [[chemistry]] to denote a repeated substructure within a molecule, e.g. HC(CH<sub>3</sub>)<sub>3</sub> ([[isobutane]]) or, similarly, to indicate the stoichiometry of ionic compounds with such substructures: e.g. Ca(NO<sub>3</sub>)<sub>2</sub> ([[calcium nitrate]]).

This is a notation that was pioneered by [[Berzelius]], who wanted chemical formulae to more resemble algebraic notation, with brackets enclosing groups that could be multiplied (e.g. in 3(AlO<sub>2</sub> + 2SO<sub>3</sub>) the 3 multiplies everything within the parentheses).{{sfn|Watts|1877|pp=140–141}}{{sfn|Ihde|1984|p=115}}

In [[chemical nomenclature]], parentheses are used to distinguish structural features and multipliers for clarity, for example in the polymer [[poly(methyl methacrylate)]].<ref>{{Cite web |title=R-0.1.5 Enclosing marks |url=https://www.acdlabs.com/iupac/nomenclature/93/r93_61.htm |access-date=3 May 2023 |website=ACDLabs.com |archive-date=3 May 2023 |archive-url=https://web.archive.org/web/20230503033434/https://www.acdlabs.com/iupac/nomenclature/93/r93_61.htm |url-status=live}}</ref>

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