> But expressions don’t mean the thing they evaluate to, this is an ad hoc meaning used in FP circles only. Is `fibonacci 1000` the integer value it evaluates to? No, it is an expression denoting the calculation of that value.

Not sure what you are talking about now.

> What’s missing from side-effect freedom or pureness? That is the property that allows replacing an expression with its value.

I think you are just unfamiliar with the terminology, that's all.

See Wikpedia again:

> If a pure function is called with arguments that cause no side-effects, the result is constant with respect to that argument list (sometimes called referential transparency or idempotence), i.e., calling the pure function again with the same arguments returns the same result. (This can enable caching optimizations such as memoization.)

(https://en.wikipedia.org/wiki/Functional_programming#Pure_fu...)

There you go. All 3 terms in once sentence. Maybe, again, you disagree with Wikipedia and the definition and that's your good right, but I don't see any point in prolonging the discussion over that.