👉 In mathematical logic, a subfix is a type of quantifier in set theory and other areas that represents a finite sequence of elements from the universe (the set or class) being quantified. It is used to specify which members of a set are included in a particular subset of its members. For example, let's say we have a set S with 3 elements {a, b, c}. In this case, we can define a subfix for the quantifier "is" as
