A metalanguage is a language used to speak about another language. The language spoken about is an object language, while the language that describes, explains, evaluates, etc. the object language is a metalanguage.
Linguistics
Linguistics is the scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying and modeling them. The traditional areas of linguistic analysis include phonetics, phonology, morphology, syntax, semantics,...