Meta-language

1. A language (the meta-language) in which another language (the object language) is described.

2. A language of higher order than the symbol system being discussed.

3. A language cannot contain a name for an expression belonging to that language. This is a rule which is necessary in order to disallow statements which are both true and false. As a rule of logic, therefore, a meta-language is required in which to name the expressions in a given object language. Statements in a meta-language are meaningless in the object language. In a meta-language, expressions can, for example, be named by using quotation marks. Thus ''John'' is a name for 'John', which is a name for John.