Not every Rustacean has a background in systems programming, nor in computer science, so we've added explanations of terms that might be unfamiliar.
Arity refers to the number of arguments a function or operation takes.
let x = (2, 3); let y = (4, 6); let z = (8, 2, 6);
In the example above
y have arity 2.
z has arity 3.