EDB — 01M

[01M] This wording is commonly used: ”let $I$ be a non-empty set of indices, and $A_i$ a family of setsCDLeng indexed by $i\in I$”; this, in axiomatic theory, should be written as ”let $I$ be a non-empty set, let $X$ be a set, and $A:I\to \mathcal{P}(X)$ a function; we will write $A_i$ instead of $A(i)$”. (With this writing we have that $A_i$ are all subsets of $X$).