What's the term to describe this combination?

Question

There are 4 items: 1, 2, 3, and 4. If we just allow the following combinations, what should we call them? I forgot it. Is it called nCr?

1 2 3 4
1 2 3
1 2 4
2 3 4
1 2
1 3
1 4
2 3
2 4
3 4
1
2
3
4

Answer 1

This is the powerset of your original set, with one exception.

The powerset of a set is the set of all possible subsets. Your list is that, except that your list does not include the empty set, which is a subset of all sets.

Answer 2

That's the power set. Note that the power set also contains the empty set.