It is not known, and the model problem for this is Hilbert's 13th [1].

Nonetheless, "elementary function" is a technical term dating back to the 19th century; it's very much not a general adjective whose synonym is "basic".

[1] https://en.wikipedia.org/wiki/Hilbert%27s_thirteenth_problem

Thanks, actually https://en.wikipedia.org/wiki/Elementary_function confirms your claim.

Nevertheless, it is a horrible definition. Mathematicians have often taken care to define things as close to everyday intuition as they could (and then proving an equivalence). The "elementary function" in this definition is just a weird mix of concerns.

Elementary function is also a general English phrase that can very much be used to represent the functions on a scientific calculator.