Editing Backus–Naur form (section)

=== Others ===
Many BNF specifications found online today are intended to be human-readable and are non-formal.  These often include many of the following syntax rules and extensions:
* Optional items enclosed in square brackets: <code>[&lt;item-x&gt;]</code>.
* Items existing 0 or more times are enclosed in curly brackets or suffixed with an asterisk (<code>*</code>) such as <code>&lt;word&gt; ::= &lt;letter&gt; {&lt;letter&gt;}</code> or <code>&lt;word&gt; ::= &lt;letter&gt; &lt;letter&gt;*</code> respectively.
* Items existing 1 or more times are suffixed with an addition (plus) symbol, <code>+</code>, such as <code>&lt;word&gt; ::= &lt;letter&gt;+</code>.
* Terminals may appear in bold rather than italics, and non-terminals in plain text rather than angle brackets.
* Where items are grouped, they are enclosed in simple parentheses.