👉 In mathematics, a pseudostratum is a type of structure that has some properties in common with a real stratum but differs from it in one or more ways. In other words, it can be considered as a subset of a real stratum, but not exactly equal to it. The term "pseudostratum" was coined by J. P. Cameron and D. G. Smith in 1967. In the context of set theory, a pseudostratum is a type