Editing Backus–Naur form (section)

==Example==
A practical illustration of BNF is a specification for a simplified U.S. [[Address (geography)|postal address]]:
<syntaxhighlight lang="bnf"><postal-address> ::= <name-part> <street-address> <zip-part>

      <name-part> ::= <personal-part> <last-name> <opt-suffix-part> <EOL> | <personal-part> <name-part>

  <personal-part> ::= <first-name> | <initial> "."

 <street-address> ::= <house-num> <street-name> <opt-apt-num> <EOL>

       <zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL>

<opt-suffix-part> ::= "Sr." | "Jr." | <roman-numeral> | ""
    <opt-apt-num> ::= "Apt" <apt-num> | ""</syntaxhighlight> 
This translates into English as: 
* A postal address consists of a name-part, followed by a [[street name|street-address]] part, followed by a [[ZIP Code|zip-code]] part.
* A name-part consists of either: a personal-part followed by a [[last name]] followed by an optional [[Suffix (name)|suffix]] (Jr. Sr., or dynastic number) and [[end-of-line]], or a personal part followed by a name part (this rule illustrates the use of [[Recursion (computer science)|recursion]] in BNFs, covering the case of people who use multiple first and middle names and initials).<ref>{{FOLDOC|Backus-Naur+Form}}</ref>
* A personal-part consists of either a [[first name]] or an [[initial]] followed by a dot.
* A street address consists of a house number, followed by a street name, followed by an optional [[apartment]] specifier, followed by an end-of-line.
* A zip-part consists of a [[town]]-name, followed by a comma, followed by a [[U.S. postal abbreviations|state code]], followed by a ZIP-code followed by an end-of-line.
* An opt-suffix-part consists of a suffix, such as "Sr.", "Jr." or a [[Roman numerals|roman-numeral]], or an empty string (i.e. nothing).
* An opt-apt-num consists of a prefix "Apt" followed by an apartment number, or an empty string (i.e. nothing).

Note that many things (such as the format of a first-name, apartment number, ZIP-code, and Roman numeral) are left unspecified here. If necessary, they may be described using additional BNF rules.