#ctor​(AngouriMath.​Entity)

This node represents the cardinality of a set: card(S) is the number of
elements of S. Counted for a finite set whose elements are numbers, and for
an interval whose ends are; left as written for an infinite set, which has a
cardinality this library has no number for, and for a set whose elements are not
yet known to be distinct.
https://github.com/asc-community/AngouriMath/issues/1212