In contact linguistics, a substratum (lat. sub: under + stratum: layer → lower layer) is a language that influences another one while that second, intrusive, language supplants it. Similarly, a superstratum is an intrusive language that exerts influence on another language. An adstratum refers to a language that's in contact with another language in a neighbour population without either identifiably having higher or lower prestige. Thus, both terms refer to a situation where an intrusive… (More on Adstratum)