I recently read a math book in which delimiters never adjusted to the size of their content or the level of nesting. This isn’t unusual in articles, but books usually pay more attention to typography.

Here’s a part of an equation from the book:

Larger outer parentheses make the equation much easier to read, especially as part of a complex equation. It’s clear at a glance that the function φ^{-1} applies to the result of the integral.

The first equation was typeset using

\varphi^{-1} ( \int \varphi(f+g) ,dmu )

The latter used `left`

and `right`

to tell LaTeX that the parentheses should grow to match the size of the content between them.

\varphi^{-1} \left( \int \varphi(f+g) ,d\mu \right)

You can use `\left`

and `\right`

with more delimiters than just parentheses: braces, brackets, ceiling, floor, etc. And the left and right delimiters do not need to match. You could make a half-open interval, for example, with `\left(`

on one side and `\right]`

on the other.

For every `\left`

delimiter there must be a corresponding `\right`

delimiter. However, you can make one of the pair empty by using a period as its mate. For example, you could start an expression with `\left[`

and end it with `\right.`

which would create a left bracket as tall as the tallest thing between that bracket and the corresponding `\right.`

command. Note that `\right.`

causes nothing to be displayed, not even a period.

The most common example of a delimiter with no mate may be a curly brace on the left with no matching brace on the right. In that case you’d need to open with `\left\{`

. The backslash in front of the brace is necessary to tell LaTeX that you want a literal brace and that you’re not just using the brace for grouping.

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