Set of Sets/Examples/Set of Arbitrary Sets 1

Example of Set of Sets
Let:

Let $\mathscr S = \set {A, B, C}$.

Then:
 * $\mathscr S = \set {\set {1, 2, 3, 4}, \set {a, 3, 4}, \set {2, a} }$

Note that none of $a, 1, 2, 3, 4$ are elements of $S$.