A superstratum or superstrate is the counterpart to a substratum. When one language succeeds another, the former is termed the superstratum and the latter the substratum. In the case of French, for example, Vulgar Latin is the superstrate and Gaulic is the substrate.
For instance, some linguists contend that Japanese consists of a Altaic superstratum projected onto an Austronesian substratum, or that the Insular Celtic languages resulted from a Celtic superstratum over an Afroasiatic substratum.
To be a substratum (and not an adstratum or a superstratum), the influence on the receiving language needs to have been substantial, something considerably more than just some borrowings or the result of a common sprachbund (an adstratum), or not the result of the dominance another language generates (a superstratum).
When the influence of another language is too remote in the past for its influence on the surviving language to be adequately characterized, 'substrate' is used by default, though the situation might have really been that of an adstratum or even a superstratum.
A superstratum or superstrate is the counterpart to a substratum.
When one language succeeds another, the former is termed the superstratum and the latter the substratum.
The Neo-Latin and Neo-Greek coinages adopted by European languages (and now, languages worldwide) to describe scientific topics (anatomy, medicine, botany, zoology, all the '-ology' words, etc.) can also be termed a superstratum, although for this last, adstratum could just as easily be used.