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Style Manual

Mathematical relationships

Words can express mathematical relationships in most content. Code mathematical expressions in specialist content so it’s accessible.

Use words instead of symbols to improve accessibility

In most content, explain mathematical relationships using words instead of symbols. This helps to ensure everyone can understand your content.

Follow rules for using numerals or words for numbers.

Write this

The square root of 56 is greater than the square root of 26.

Not this

√56 > √26.

Use code for symbols, not punctuation

Use mathematical symbols and equations if research shows they are needed by users.

When you use symbols in equations:

  • put a non-breaking space between the number and adjacent symbols
  • use the right character for the operators (+, ‐, ×, ÷)
  • set equations as a block quote.

Seek professional advice for the correct markup for specialist content.

Accessibility requirements

Mathematical expressions often contain symbols and superscript. Superscript is a number, letter or symbol placed above a character, for example, the ‘2’ in ‘x2’.

Unless they are coded correctly, symbols and superscript may be inaccessible for some people who:

  • have low vision
  • use screen readers to access content.

Insert symbols and superscript with tools such as:

These make mathematical equations and symbols accessible, including for screen readers.

Ensure both symbols and superscript can be enlarged without loss of content or functionality. Don’t use images of symbols or superscript.

Resources:

WCAG quick reference: 1.3.1 Info and relationships – level A

Spacing

For equations, there must be a non-breaking space between the number and adjacent symbols.

Correct

10 + 1 = 11

Incorrect

10+1=11

Don’t insert a space into ratios. Ratios do not involve a symbol, unlike mathematical operators. Use a colon.

Correct

5∶1

Incorrect

5 ∶ 1

Negative numbers and subtraction

Use the mathematical symbol for minus. Don’t use an en dash instead.

In Unicode, the minus symbol is U+2212.

The minus symbol is:

  • spaced to show subtraction in an equation (for example 8 − 4)
  • unspaced to show a negative number (for example −4).

To show a negative value, write the number after the minus sign without a space.

Correct

−5

Incorrect

− 5

Division and multiplication

You can use the division symbol (÷) or the division slash () to show division. People sometimes use the forward slash (/) to show division as well.

In most cases, it's best to use the division symbol (÷). The division slash is easily confused with the forward slash which is also used to show alternatives.

In Unicode, the division symbol is U+00F7 and the division slash is U+2215.

Use the mathematical symbol for multiply (×). Don’t use the letter ‘x’.

In Unicode, the multiplication symbol is U+00D7.

Example

(x + y)÷(a + b)

(x + y)(a + b)

(x + y)×(a + b)

Release notes

The digital edition revises guidance on the expression of mathematical relationships.

It deviates from advice in the sixth edition in several instances. It recommends using words rather than numbers as the default choice, except for precise relationships. The sixth edition advised words were an option for non-exact mathematical relationships.

The digital edition also advises against using the en dash for a minus sign.

The digital edition includes advice about the division symbol, which was not in the sixth edition.

The Content Guide did not cover this topic.

About this page

Evidence

American Psychological Association (2020) ‘Statistical and mathematical copy’, Publication manual of the American Psychological Association, 7th edn, American Psychological Association, Washington DC.

Barstow C and Rothberg M (2004) ‘1.11 Mathematics’, IMS guidelines for developing accessible learning applications, IMS Global Learning Consortium website, accessed 3 June 2020.

GOV.UK (2016) ‘A-to-Z: numbers’, Style guide, GOV.UK, accessed 3 June 2020.

References

Ausbrooks R, Buswell S, Carlisle D, Chavchanidze G, Dalmas S, Devitt S, Diaz A, Dooley S, Hunter R, Ion P, Kohlhase M, Lazrek A, Libbrecht P, Miller B, Miner R,  Rowley C, Sargent M, Smith B, Soiffer N, Sutor R and Watt S (2014) ‘Mathematical Markup Language (MathML) version 3.0 2nd edition’, W3C recommendation, W3C website, accessed 20 May 2020.

>Bohman P (20 January 2014) ‘Why don’t screen readers always read what’s on the screen? Part 1: punctuation and typographic symbols’, deque blog, accessed 20 May 2020.

LaTeX Project Team (2018) User’s guide for the amsmath package (version 2.1) [PDF 443 KB], American Mathematical Society, LaTeX 3 Project, accessed 4 June 2020.

Microsoft Corporation (2019) Keyboard shortcuts in Word: insert international characters, Microsoft website, accessed 4 June 2020.

Owen M (2018), How to type accented letters in macOS three different ways, appleinsider website, accessed 4 June 2020

The LaTeX Project (n.d.) An introduction to LaTeX, The LaTeX Project website, accessed 4 June 2020.

The Unicode Consortium (2020) ‘Mathematical operators’, Unicode 13.0 character code charts, Unicode website, accessed 4 June 2020.

WHATWG (Web Hypertext Application Technology Working Group)(2020) ‘4.8.16: MathML’, HTML: living standard, WHATWG website, accessed 4 June 2020.

This page was updated Monday 28 September 2020.

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