In a formal description of a computer language, it is often convenient to use a more precise language than English. This language-description language is referred to as a metalanguage. The metalanguage which will be used to describe the C language is that specified by British Standard 6154. A tutorial introduction to the standard syntactic metalanguage is available from the National Physical Laboratory.

The BS6154 standard syntactic metalanguage is similar in concept to many other metalanguages, particularly those of the well-known Backus-Naur family. It therefore suffices to give a very brief informal description here of the main points of BS6154; for more detail, the standard itself should be consulted.