abstract:A metasyntax describes the allowable structure and composition of phrases and sentences of a metalanguage, which is used to describe either a natural language or a computer programming language. Some of the widely used formal metalanguages for computer languages are Backus–Naur Form (BNF), Extended Backus–Naur Form (EBNF), Wirth syntax notation (WSN), and Augmented Backus–Naur Form (ABNF).