I don’t think I have ever seen ∋ used to mean “such that” so I was very confused until I got to the explanation (as it were; why CONTAINS AS MEMBER is being used to mean “such that” is never explained).

as a math major i had the same confusion; for such that i use "s.t.". but apparently peano used ∋ to mean such that:

https://math.stackexchange.com/questions/15455/backwards-eps...

Same. I recalled pipe being used for "such that". But [per wikipedia](https://en.wikipedia.org/wiki/Glossary_of_mathematical_symbo...), that's specifically "set-builder notation", and the _last one_ of the twelve instances of the string "such that" on the page (though I don't know if they're ordered by usage, "alphabetically", or what).

Interesting, my experience in classes using set theory was the opposite, where ∋ only meant “such that” and ∈ only meant “is a member of”.

Learning programming syntax at the same time made it frustrating to learn that math symbols were less strictly defined and less universal, that it was best to write proofs/derivations/etc in plain English in many cases instead of the neat symbols

It also doesn't make much sense

> There exists a raven such that the vector of hours.

The vector of hours what?

This isn't quite what's going on. A better reading might be "which is a";

"Ǝx s.t. x∈ℕ" (there exists an x such that x is in the naturals) is just being shortened to "Ǝx∋ℕ" (there exists an x in the naturals), or there exists an x which is in the naturals.

It's not really that different from the normal usage.