That is, if a function's arity is the number of inputs it has, its __ is the number of outputs it has. (Fill in the blank.)
I am pretty sure, based on a Google search, that at least some people call this notion "coarity" (or "co-arity" if you want the pronunciation to be clearer).
A function is a mapping from elements in one set to another set. The "from" set is called the domain, and the "to" set is called the range.
We can also combine sets to create multi-dimensional sets
It also makes sense to talk about functions mapping from a set of tuples to a set of tuples.
tl;dr When you talk about functions which outputs mulitple arguments, you're really talking about functions which outputs a single element which is an n-tuple.