# Delimiters

Delimiters are objects which act logically like parentheses. These can
be used only in math mode.
The delimiters recognized by LaTeX include

`(` (left parenthesis)
`)` (right parenthesis)
`[` (left bracket)
`]` (right bracket)
`\{` (left brace)
`\}` (right brace)
`|` (vertical line)
`\vert` (vertical line)
`\|` (double vertical lines)
`\Vert` (double vertical lines)
`/` (slash)
`\backslash` (backslash)
`\langle` (left angle bracket)
`\rangle` (right angle bracket)
`\uparrow` (uparrow)
`\downarrow` (down arrow)
`\updownarrow` (up/down arrow)

Delimiters in formulas should be big enough to "fit" around the formulas
they delimit (for example arround arrays).
To obtain "stretchable" delimiters (LaTeX makes them the
appropriate size) type a `\left` or `\right` command before
the delimiter. `\left` and `\right` commands must come in
matching pairs, although the delimiters themselves need not be the same.
Thus, \left \{ ... \right \[

produces a legal pair.
In cases where only one delimiter is desired, it
is possible to make the matching delimiter "invisible" by typing a
period (`.`) after the command, i.e.,
`\left.` or `\right.`.
## Some examples

### A six-j symbol

`\[ \left\{
\begin{array}{ccc}
a & b & c \\
d & e & f \end{array}
\right\} \]`

This should be displayed something like (insofar as it can be rendered in
"ascii art"):
( a b c )
- -
( d e f )

Note that the `\[ ... \]` set this off as
Display Math, and that the Array Environment
is used to generate the three centered columns inside the braces.
### A "multiple choice" equation

`\[ f(x) =
\left\{ \begin{array}{l}
0, x < 0 \\ 1, x = 0 \\
2, x > 0 \end{array} \right. \]`

will be displayed as
` ( 0, x < 0
f(x) = - 1, x = 0
( 2, x > 0`

Note that the "invisible" `\right` delimiter is specified using
a "period".

Related topics:

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Sheldon Green, agxsg@giss.nasa.gov, 17 May 1995.