superstratum; superstrate
In linguistics, a language that influences another from a position of higher prestige, often leaving loanwords and structural features in the substrate language.
French left many vocabulary items as a superstratum in English.
The influence of a superstratum can extend not only to loanwords but also to grammar.
傍層語 (adstratum) refers to a language of equal prestige that influences another through contact, distinct from the hierarchical relationship implied by 上層語.
Compound of 上層 (じょうそう, 'upper layer') + 語 (ご, 'language'), calque of English 'superstratum'.