Both substratum and superstratum languages influence each other, but in different ways. An adstratum or adstrate is a language that is in contact with another language in a neighbor population without having identifiably higher or lower prestige. The notion of "strata" was first developed by the Italian linguist Graziadio Isaia Ascoli (1829–1907), and became known in the English-speaking world through the work of two different authors in 1932.[1]