View Single Post
CRGreathouse
#3
Jan11-10, 09:16 AM
Sci Advisor
HW Helper
P: 3,684
Quote Quote by Kyouran View Post
So here is my question: Can we actually speak of "the number of elements in a set"?
Yes.

You might consider comparing the notion of "set" to those of "multiset" (sometimes called "bag") and "tuple". Sets don't allow duplicates ({1} = {1, 1}) and don't consider order ({1, 2} = {2, 1}); multisets allow duplicates ({1} ≠ {1, 1}) and don't consider order ({1, 2} = {2, 1}); tuples allow duplicates ((1) ≠ (1, 1)) and consider order ((1, 2) ≠ (2, 1)).