This page describes how to format common mathematical notation such as exponents, expressions, equations, operators, and variables in documentation. Formatting best practices can help ensure that your documentation is compatible with assistive technologies and renders accurately.
For general information about using and formatting numbers, see Numbers.
Note: This page includes examples of formatting in HTML and Markdown in standard text. If you're using a third-party tool to display complex math, follow that tool's formatting guidance to ensure that your mathematical markup displays correct.
Use HTML entities for mathematical symbols
In general, use HTML entities for mathematical symbols instead of keyboard
symbols. The following table lists entities for symbols that are common in
arithmetic and algebra. For the plus sign (+), equals sign
(=), and division sign (/), you can use
their keyboard equivalents.
| Symbol | Markup | Description |
|---|---|---|
| + | Use the keyboard symbol. | Plus sign |
| − | − |
Minus sign |
| × | × |
Multiplication sign Alternatively, you can use the dot operator You can indicate multiplication by omitting the multiplication symbol if doing so doesn't create ambiguity—for example, instead of a × b, you can write ab. |
| / | Use the keyboard symbol. | Division sign |
| = | Use the keyboard symbol. | Equals sign |
| ≠ | ≠ |
Not equal to |
| ± | ± |
Plus-minus sign |
| ∓ | ∓ |
Minus-plus sign |
| < | < |
Less than sign |
| > | > |
Greater than sign |
| ≈ | ≈ |
Approximately equal to |
| ≉ | ≉ |
Not approximately equal to |
| ≅ | ≅ |
Congruent to |
| ≤ | ≤ |
Less than or equal to |
| ≥ | ≥ |
Greater than or equal to |
| ≡ | ≡ |
Identical to |
| ≢ | ≢ |
Not identical to |
| √ | √ |
Square root |
| ∑ | ∑ |
N-ary summation |
Format mathematical notation
The following sections provide formatting for common math-related notation.
Operators
To ensure accessibility and accurate HTML syntax, use
HTML entities
instead of keyboard symbols for operators. For example, use
− instead of a hyphen (-).
Include a non-breaking space ( ) on both sides
of operators within a single expression, equation, or
statement.
Don't italicize operators.
Recommended: a − b
To render a − b, use the following markup:
- HTML:
<i>a</i> − <i>b</i> - Markdown:
_a_ − _b_
Variables
Italicize variables.
Recommended: x ≠ y
Recommended: xy
Recommended: yi
To render x ≠ y, use the following markup:
- HTML:
<i>x</i> ≠ <i>y</i> - Markdown:
_x_ ≠ _y_
Expressions and equations
Include short expressions and equations inline with your text.
Include a non-breaking space ( ) between components
such as operators and variables so that the expression or equation renders on
the same line.
When an expression or equation creates an awkward line break, consider placing it on its own line.
Recommended: The equation that describes a linear trend line is y = a + bx.
Recommended: The equation that describes a polynomial trend line, where the order is o, is the following: y = a + b × x + ... + k × xo
To render y = a + bx, use the following markup:
- HTML:
<i>y</i> &= <i>a</i> + <i>bx</i> - Markdown:
_y_ &= _a_ + _bx_
Fractions
Express fractions as decimal numbers, when possible.
If you must express fractions as words, connect the numerator and denominator with a hyphen unless one of them is already hyphenated.
Recommended: 0.02
Recommended: one and one-half
Recommended: three-sevenths
Recommended: three seventy-fourths
Exponents and subscripts
Use standard mathematical notation. Don't put a space between the base and the exponent.
To render exponents, use the HTML <sup> tag. Don't use the
keyboard caret symbol (^) to indicate an exponent.
To render subscripts, use the HTML <sub> tag.
Recommended: 23
Recommended: xy
Recommended: yi
Not recommended: 2^3
To render 23, use the following markup in HTML and Markdown:
2<sup>3</sup>
Notation as words
In general, you can use mathematical notation in place of words in running text. For example, in a sentence, you might use the statement x ≠ y instead of writing "x is not equal to y." If the use of notation instead of words creates ambiguous, grammatically incorrect, or difficult-to-read text, then use words to convey the mathematical concept.
Recommended: Check whether a > b.
Recommended: The area is calculated by multiplying the length by the width.
Not recommended: Check whether a is greater than b.
Not recommended: The area is calculated by multiplying l × w.
Provide visuals for math concepts
Accompany math concepts and numerals with diagrams or other images to support comprehension. For example, if comparing statistics, consider illustrating percentages in a pie chart or a bar graph.