Definition:Metalanguage

General Definition
A metalanguage is a language (either formal or natural) which is used to make statements about another language (again, either formal or natural).

Formal Systems
In the context of formal systems, a metalanguage is a formal language used to specify another formal language.

Object Language
The object language of a metalanguage is the language it describes.

Metasyntax
The syntax of the metalanguage is called a metasyntax of the object language.

In some contexts the metalanguage itself is referred to as a metasyntax.

Note that it is "a metasyntax" as a given object language may have multiple metalanguages to define it.

Metasymbol
A metasymbol is a symbol used in a metalanguage to represent an arbitrary word in the object language.

Altenative terms for this are metalogical variable or metasyntactic variable.