Learn English – Defining a goal that can be achieved through many ways

There are many existing terms for a number possible concepts that you might be using:

• if you are talking about a question/situation that has one outcome (functional) out of many distinct choices, like one out of many but a finite set of colors, then it is discrete or nominal (the latter technical for statistics).
• if you are considering a situation where you get many results at once, like red, blue, and green together from the rainbow, then it is multivalued, a subset, a tuple, or n-ary (the latter 3 are technical). 'n-ary' is probably not in any nontechnical dictionary but is in wide use in mathematical language.

There's a lot of technical math vocabulary that may or may not be appropriate in informal conversation; one can consider the kinds of values returned (as in computer programming the type like boolean, int, or real) and also the number of different values returned (for a person - height, eye color, handedness). Here is a small taxonomy:

• number of values returned
  • single value = functional
  • multiple value = relational (or multivalued)
    • a given set number of values returned is fixed arity
    • variable being n-ary or polyadic (multivariate for arguments, __multivalued for results),
• the range/possibilities of a given single value
  • continuous
  • discrete, and discrete has a number of words to describe variations (binary, boolean, dichotomous, nominal, integral, combinatorial)

You might just say lesser-known. Words like exotic and arcane can be construed as mildly offensive.

Edit: For what it's worth, a quick search reveals that this is actually a category used by the US Library of Congress. I also ran into it on McGill's linguistics website.