Acronym for Backus Naur Form.
<sentance> ::= <verb-part> <noun-part>
<verb-part> ::= <noun-part> <verb>
<noun-part> ::= <proper-noun>
| THE <noun>
<verb> ::= throws
| kicks | hides | fetches
<proper-noun> ::= John
| Jane
<noun> ::= ball
::= dog
This would accept sentances such as
John kicks the dog Jane throws the ball The dog fetches the ball
There are usually several extensions to BNF which are often used, often called "EBNF". EBNF has "..." for "1 or more" and "[?" for optional
2 pages link to BNF: