Bracketing in Mathematical Expressions

When the shape of the brackets does not have notational meaning, it is conventional to work outward in the sequence { [ ( ) ] }. Nesting of plain parentheses should be avoided.

Large bracketing should be used to surround built-up fractions in displayed equations; one may then start the sequence again.

When the argument of a function contains parentheses, it is preferred to enclose it in bold parentheses instead of square brackets:

$\Gamma$($\frac{1}{2}(x+y)$)

However, it is customary to use square brackets for functional notation:

$E[\rho(r)]$

Use enough bracketing to make the meaning clear and unambiguous. Be especially clear with fractions formed with the solidus (/). According to accepted convention, all factors appearing to the right of a solidus are to be construed as belonging in the denominator: for example,

$\begin{align} a/bf(x) & = a/[bf(x)] \\ & = \frac{a}{bf(x)} , \\ \frac{a}{b} f(x) & = (a/b)f(x) , \\ \end{align}$

but

$sin \theta/2 =?$

If there is another way that avoids both the ambiguity and the extra bracketing, that is usually the better way.

Use	Rather than
$e^{−x}/f(x)$	$[exp(−x)]/f(x)$
sin $\frac{1}{2}\theta$	sin$(\theta/2)$
$\frac{1}{2}sin\theta$	$(sin\theta)/2 or (1/2) sin\theta$

Put in extra bracketing even where convention does not require it, if a likely misreading is thereby avoided. But leave them out where they would merely clutter the picture.

Use	Rather than
$sin \omega{t}$	$sin(\omega{t})$
$\frac{1}{2}a$	$(1/2)a$
$2.0 ± 0.2 mm/s$	$(2.0 ± 0.2) mm/s$
$MeV^2$	$(MeV) ^2$

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