October 1995
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,
but
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 |
| $sin \omega{t}$ | $sin(\omega{t})$ |
| $\frac{1}{2}a$ | $(1/2)a$ | $2.0 ± 0.2 mm/s$ | $(2.0 ± 0.2) mm/s$ | $MeV^2$ | $(MeV) ^2$ |