(Not the author) I presume a reference to one the many mathematical/scientific usages? https://en.wikipedia.org/wiki/Xi_(letter)#Mathematics_and_science https:/

(Not the author) I presume a reference to one the many mathematical/scientific usages? https://en.wikipedia.org/wiki/Xi_(letter)#Mathematics_and_science https://en.wikipedia.org/wiki/Xi_(letter)#Mathematics_and_sc... I particularly like the "No change of state" meaning in "Z notation", apparently a formal language for specifying and modeling computer systems. Edit: never mind, author beat me and debunked my overly-complicated analysis