Complex sentence: Metalinguistics is used to refer to the language, whether natural or formalized (as in logic), which is itself used to speak of language; to a language whose sole function is to describe a language.
Split into simpler sentences: Metalinguistics is used to refer to the language, whether natural or formalized (as in logic), which is itself used to speak of language. Metalinguistics refers to a language whose sole function is to describe a language.