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division signs more formally

The division sign most commonly seen in school as ÷ is called the obelus , but in more formal mathematics it is usually replaced by a slash, a fraction bar, or a colon, depending on context.

What “division signs” actually are

  • The obelus (÷) is a short horizontal line with a dot above and below, historically adopted for division in the 17th century and widely used in elementary arithmetic.
  • Modern standards for scientific and technical writing explicitly discourage using ÷ and instead recommend a solidus (slash /), a fraction bar (horizontal line in stacked fractions), or sometimes a colon (:) for ratios.
  • Calculators and school worksheets still often use ÷ because it is visually clear for beginners, even though it is not preferred in higher-level or formal math writing.

More formal ways to write division

When writing “more formally,” mathematicians generally prefer:

  • Fraction bar :
    • Example: 62\frac{6}{2}26​ instead of 6÷26÷26÷2.
* This is the standard in textbooks and papers because it shows clearly what is in the numerator and denominator.
  • Solidus (slash /) :
    • Example: 6/26/26/2 in plain text or programming contexts.
* Often used where typesetting a proper fraction bar is inconvenient.
  • Colon (:) for ratios :
    • Example: a:ba:ba:b for “the ratio of aaa to bbb,” which is conceptually related to division but usually read as a ratio, not a direct division command.

In formal standards like ISO 80000‑2, the recommendation is:

  • Use / or a fraction bar for division.
  • Use : for ratios.
  • Do not use ÷ for division.

When to avoid the obelus (÷)

In more advanced or professional contexts, ÷ is usually avoided because:

  • It can be ambiguous in complex expressions; a fraction bar makes groupings clearer.
  • It has been used for different meanings in some European countries (e.g., negation or ranges), which can cause confusion.
  • Formal standards bodies explicitly advise against its use in scientific notation.

So if you want to be “more formal,” write division as a fraction or with a slash , and reserve ÷ mainly for elementary-level or informal contexts.

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