Metalanguage

In semantics, the metalanguage is the language that is used to talk about (expressions of) another language, the object language.

Comments
Object language and metalanguage can be the same, e. g. ordinary English, but they always differ in function. If we cannot detect any metalanguage in a sentence, there is no object language either. The distinction was introduced to avoid the liar's paradox.

Link
Utrecht Lexicon of Linguistics

Reference
Gamut, L.T.F. (1991) Logic, language, and meaning, Univ. of Chicago Press, Chicago.

Other languages
German Metasprache