Can “if" and "iff” be interchanged with “when" and "whenever” respectively?

Question

Let $A$ and $B$ be arbitrary sets and consider the following two statements: \begin{gather} (x\in A)\Rightarrow (x\in B)\\ (x\in A)\Leftrightarrow (x\in B) \end{gather}

These two statements are usually worded as follows:

1. If $x$ belongs to $A$, then $x$ belongs to $B$”
2. “$x$ belongs to $A$ if and only if $x$ belongs to $B$”.

My questions are:

1. Can the first statement be read as “$x$ belongs to $A$ when $x$ belongs to $B$”?
2. Can the second statement be read as “$x$ belongs to $A$ whenever $x$ belongs to $B$”?

So, is it possible to use “when” instead of “if” and “whenever” instead of “if and only if”?

Answer 1

The words "when" and "whenever" can be used interchangeably in this context. In both cases the words can be interchanged with the word "if". This means that neither of these are suitable to be used instead of "iff".

If you want to find a suitable replacement for "iff", then there are a few options. Some include "exactly when" or "precisely if". You could also say "$A$ is necessary and sufficient for $B$" as an alternative for $A$ iff $B$.

For a more complete list of alternatives, you may want to check out some of the answers to this question on alternative ways to say "if and only if" which provides some additional options that you could use.